{"id":10562,"date":"2022-06-08T16:58:07","date_gmt":"2022-06-08T14:58:07","guid":{"rendered":"https:\/\/www.plantcaretools.com\/lichtintensiteit-meten-planten\/"},"modified":"2026-11-02T20:09:19","modified_gmt":"2026-11-02T19:09:19","slug":"measure-light-intensity-plants","status":"publish","type":"page","link":"https:\/\/www.plantcaretools.com\/en\/measure-light-intensity-plants\/","title":{"rendered":"Measure light intensity for plants"},"content":{"rendered":"\n<div class=\"pct-kb-hero\">\n<svg class=\"pct-kb-leaf\" viewBox=\"0 0 200 300\" aria-hidden=\"true\"><path fill=\"#2d5a27\" d=\"M100 5C30 70 10 170 100 295 190 170 170 70 100 5Z\"\/><path stroke=\"#eaf4e8\" stroke-width=\"4\" fill=\"none\" d=\"M100 20V290M100 90l-40-30M100 140l-55-35M100 190l-55-30M100 90l40-30M100 140l55-35M100 190l55-30\"\/><\/svg>\n<div class=\"pct-kb-hero-inner\">\n<div class=\"pct-kb-hero-left\">\n<div class=\"pct-kb-badge\">Knowledge base \u00b7 Measure light intensity<\/div>\n<h1 class=\"pct-kb-title\">Measure light intensity: how many <span class=\"pct-accent\">lux<\/span> does your plant need?<\/h1>\n<p class=\"pct-kb-desc\">Measure light intensity at leaf height, right where your plant stands. Here you can read how many lux your plant needs, how to read a light meter and why your phone only gives a rough estimate.<\/p>\n<div class=\"pct-kb-meta\"><span><b>Updated<\/b> 2026<\/span><span><b>Reading time<\/b> 5 minutes<\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n<style>\n.pct-kb-hero,.pct-kb-hero *{box-sizing:border-box}\n.pct-kb-hero{width:100vw;max-width:100vw;margin-left:calc(-50vw + 50%);margin-right:calc(-50vw + 50%);margin-top:0;background:linear-gradient(135deg,#eaf4e8 0%,#d6edcc 60%,#c5e8be 100%);padding:56px 5% 64px;position:relative;overflow:hidden}\n.pct-kb-hero-inner{max-width:1100px;margin:0 auto;display:flex;align-items:center;gap:48px;position:relative;z-index:1}\n.pct-kb-hero-left{flex:1 1 440px;min-width:0}\n.pct-kb-leaf{position:absolute;left:-150px;top:50%;transform:translateY(-50%) 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(max-width:767px){.pct-kb figure.pct-kb-img{max-width:220px}.pct-kb figure.pct-kb-img img{max-height:200px}}\n<\/style>\n<script>(function(){function l(){document.querySelectorAll(\".pct-kb-table table\").forEach(function(t){var h=[].map.call(t.querySelectorAll(\"thead th\"),function(x){return x.textContent.trim()});t.querySelectorAll(\"tbody tr\").forEach(function(r){[].forEach.call(r.children,function(c,i){if(h[i])c.setAttribute(\"data-label\",h[i])})})})}if(document.readyState!==\"loading\")l();else document.addEventListener(\"DOMContentLoaded\",l)})();<\/script>\n<script type=\"application\/ld+json\" id=\"pct-kb-faq-schema\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"@id\":\"https:\/\/www.plantcaretools.com\/en\/measure-light-intensity-plants\/#faq\",\"inLanguage\":\"en\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"How many lux do plants need?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"It depends on the plant. Low-light plants manage with 540 to 2,700 lux, medium-light plants need 2,700 to 10,800 lux and high-light plants want more than 10,800 lux (University of Minnesota). Below about 540 lux, hardly any plant survives for long.\"}},{\"@type\":\"Question\",\"name\":\"How much light does a monstera need?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"A monstera is a medium-light plant: between 2,700 and 10,800 lux. A spot close to an east or west window therefore usually works well. Strong midday sun behind glass, however, can scorch the leaves.\"}},{\"@type\":\"Question\",\"name\":\"How many lux is sunlight?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Outdoors in full sun you measure more than 100,000 lux. Indoors it is much less, because glass, curtains and the distance from the window block light. A few metres from the window you often measure only a tenth of the value right next to the glass.\"}},{\"@type\":\"Question\",\"name\":\"How do I know if my plant gets too little or too much light?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"With too little light, leaves turn pale or yellow, stems become long and thin and the leaves grow further apart. Variegated leaves may also turn completely green, and flowering plants form no buds. Too much light shows as scorched or bleached patches on the leaves (University of Minnesota).\"}},{\"@type\":\"Question\",\"name\":\"Can I use a light meter app for plants?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"For a first impression, yes, but do not expect an exact number. In one test, a phone\u2019s light sensor was up to almost 40% off without calibration, and in low light (below 100 lux) even more than 60%. A separate light sensor was only 2.7% off in the same test (Gutierrez-Martinez et al., 2017). If you really want to choose a spot, use a light meter.\"}},{\"@type\":\"Question\",\"name\":\"What is the difference between lux and PPFD?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Lux measures how bright light looks to the human eye. PPFD, on the other hand, counts the light particles a plant uses for photosynthesis, in \u00b5mol per square metre per second. For research and growing, PPFD is therefore the better measure (Virginia Tech). To compare spots in your home in daylight, lux is fine.\"}},{\"@type\":\"Question\",\"name\":\"How do I convert lux to PPFD?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"In daylight, divide the number of lux by 54. So 10,800 lux is roughly 200 \u00b5mol\/m\u00b2\/s. Other lamps use a different factor, for example 74 for fluorescent light (Apogee Instruments). There is no fixed factor for LED grow lights, so use the PPFD stated by the manufacturer instead.\"}},{\"@type\":\"Question\",\"name\":\"How many hours of light do plants need under a grow light?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Foliage plants need 12 to 14 hours of light a day, flowering plants 14 to 16 hours and seedlings 16 to 18 hours (University of Minnesota). Use a timer, so the plant also gets a rest every night.\"}},{\"@type\":\"Question\",\"name\":\"How far should a grow light be from plants?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"As a guideline, hang the lamp 30 to 60 cm (12 to 24 inches) above foliage plants, 15 to 30 cm (6 to 12 inches) above flowering plants, herbs and lettuce, and 10 to 15 cm (4 to 6 inches) above seedlings (University of Minnesota). Then measure at leaf height and adjust the lamp until the value suits your plant.\"}}]}<\/script>\n\n\n\n<div class=\"wp-block-group pct-kb is-layout-flow wp-block-group-is-layout-flow\"><span><span><a href=\"https:\/\/www.plantcaretools.com\/en\/\">Home<\/a><\/span><\/span>\n\n\n\n<h2 class=\"wp-block-heading\">Why it pays to measure light intensity instead of guessing<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">If you measure light intensity, you get a far more reliable answer than your eyes can give. Your eyes adapt, so a room feels bright while a plant gets too little light. Indoors, light also drops quickly. According to Mississippi State University, light intensity can fall from more than 10,000 to about 1,000 lux within a few metres of the window. A spot one metre further away may therefore need a completely different plant.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A light meter for plants shows within seconds how much light really reaches a spot. That way you choose the right plant for the spot, or the right spot for the plant. You also see straight away whether a grow light is needed. A plant that gets too little light becomes long and leggy, gets pale leaves and does not flower (University of Minnesota).<\/p>\n\n\n\n<figure class=\"wp-block-image size-large pct-kb-img\"><img decoding=\"async\" src=\"https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/19_PO220607-PLANT-CARE-TOOLS4731.jpg\" alt=\"Measure light intensity with a digital light meter showing lux and temperature\"\/><figcaption class=\"wp-element-caption\">Measure light intensity at leaf height, with the sensor facing the light.<\/figcaption><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">How many lux do plants need?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Houseplants are divided into three light groups. The University of Minnesota gives the values in foot-candles. We converted them to lux, the unit most light meters show (1 foot-candle is 10.76 lux).<\/p>\n\n\n\n<figure class=\"wp-block-table pct-kb-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Light group<\/th><th>Lux<\/th><th>PPFD<\/th><th>Examples<\/th><\/tr><\/thead><tbody><tr><td>Low light<\/td><td>540 \u2013 2,700<\/td><td>50\u2013150<\/td><td>ZZ plant, snake plant, pothos<\/td><\/tr><tr><td>Medium light<\/td><td>2,700 \u2013 10,800<\/td><td>150\u2013250<\/td><td>Monstera, ficus, spider plant<\/td><\/tr><tr><td>High light<\/td><td>more than 10,800<\/td><td>250\u2013450<\/td><td>Cacti, succulents, herbs<\/td><\/tr><\/tbody><\/table><figcaption class=\"wp-element-caption\">PPFD in \u00b5mol\/m\u00b2\/s. Source: University of Minnesota Extension, converted to lux. Below about 540 lux, hardly any plant survives for long (Mississippi State University). If you measure on a sunny afternoon, your values will be higher than in the morning or on a cloudy day.<\/figcaption><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">How many lux is daylight?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Outdoors in full sun you measure more than 100,000 lux. Full sun gives about 2,000 \u00b5mol\/m\u00b2\/s (Virginia Tech), and in daylight 1 \u00b5mol\/m\u00b2\/s equals roughly 54 lux (Apogee Instruments). Behind glass and away from the window, only part of that remains. That is why a meter with a range up to 200,000 lux, such as our <a href=\"https:\/\/www.plantcaretools.com\/en\/?attachment_id=5983\">digital light meter<\/a>, is more than enough indoors and outdoors.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Measure light intensity: how to read the result by type of meter<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Not every meter shows lux. So first check which type you have:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Lux light meter<\/strong>, such as the <a href=\"https:\/\/www.plantcaretools.com\/en\/?attachment_id=5983\">digital light meter<\/a>: compare the number with the table above. With the UNIT button you can also switch to foot-candles.<\/li>\n\n\n\n<li><strong>Plant sensor with app<\/strong>, such as the <a href=\"https:\/\/www.plantcaretools.com\/en\/?attachment_id=5769\">4 in 1 Bluetooth Plant Care Monitor<\/a>: the free Flower Care app shows light intensity on your phone, together with moisture, temperature and nutrients.<\/li>\n\n\n\n<li><strong>Soil tester with a light scale<\/strong>, such as the <a href=\"https:\/\/www.plantcaretools.com\/en\/4-in-1-soil-tester\/\">4-in-1 soil tester<\/a> and the <a href=\"https:\/\/www.plantcaretools.com\/en\/6-in-1-digital-tester-for-soil-and-liquids-ph-ec-light-moisture-fertiliser-and-temperature\/\">6-in-1 digital tester<\/a> (9 steps from weak to strong): these give an indication, not lux. Use the scale from the manual, which you can find under <a href=\"https:\/\/www.plantcaretools.com\/en\/download-manuals\/\">download manuals<\/a>.<\/li>\n\n\n\n<li><strong>Phone app<\/strong>: handy for a first impression, but less accurate. Read more about this in the questions below.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">How to measure light intensity in 4 steps<\/h2>\n\n\n\n<ol class=\"wp-block-list pct-kb-steps\">\n<li><strong>Measure at leaf height<\/strong>, exactly where the plant stands or will stand. Point the sensor towards the window or the lamp.<\/li>\n\n\n\n<li><strong>Measure at different times<\/strong>, for example in the morning, around midday and late in the afternoon. That way you see how the light changes during the day.<\/li>\n\n\n\n<li><strong>Measure on a sunny and on a cloudy day.<\/strong> One reading says little, because the average is what counts.<\/li>\n\n\n\n<li><strong>Measure again when the seasons change.<\/strong> Trees in leaf block light in summer and let more through in winter (University of Illinois).<\/li>\n<\/ol>\n\n\n\n<h2 class=\"wp-block-heading\">Light meter, plant sensor or soil tester: which suits you?<\/h2>\n\n\n\n<figure class=\"wp-block-table pct-kb-table pct-kb-compare\"><table class=\"has-fixed-layout\"><thead><tr><th><\/th><th>Light meter<\/th><th>Plant sensor<\/th><th>Soil tester<\/th><\/tr><\/thead><tbody><tr><td>Result<\/td><td>Number in lux on the display<\/td><td>Values in the app on your phone<\/td><td>Indication from weak to strong<\/td><\/tr><tr><td>Also measures<\/td><td>Temperature<\/td><td>Moisture, temperature, nutrients<\/td><td>pH, moisture, temperature<\/td><\/tr><tr><td>Stays with the plant<\/td><td>No, you measure wherever you like<\/td><td>Yes<\/td><td>No<\/td><\/tr><tr><td>Best for<\/td><td>Choosing a spot, setting up a grow light<\/td><td>Following one plant continuously<\/td><td>A quick all-round check<\/td><\/tr><tr><td>Example<\/td><td><a href=\"https:\/\/www.plantcaretools.com\/en\/?attachment_id=5983\">Digital light meter<\/a><\/td><td><a href=\"https:\/\/www.plantcaretools.com\/en\/?attachment_id=5769\">4 in 1 Bluetooth Plant Care Monitor<\/a><\/td><td><a href=\"https:\/\/www.plantcaretools.com\/en\/4-in-1-soil-tester\/\">4-in-1 soil tester<\/a>, <a href=\"https:\/\/www.plantcaretools.com\/en\/6-in-1-digital-tester-for-soil-and-liquids-ph-ec-light-moisture-fertiliser-and-temperature\/\">6-in-1 tester<\/a><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">If you mainly want to know whether a spot gets enough light, choose the <a href=\"https:\/\/www.plantcaretools.com\/en\/?attachment_id=5983\">digital light meter<\/a>. It shows lux with a range up to 200,000 lux. If you also want to follow moisture and nutrients, the <a href=\"https:\/\/www.plantcaretools.com\/en\/?attachment_id=5769\">4 in 1 Bluetooth Plant Care Monitor<\/a> is more convenient, because it simply stays with the plant.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Our recommendations to measure light intensity<\/h2>\n\n\n<div data-block-name=\"woocommerce\/handpicked-products\" data-columns=\"4\" data-content-visibility=\"{&quot;title&quot;:true,&quot;price&quot;:true,&quot;rating&quot;:false,&quot;button&quot;:false}\" data-orderby=\"menu_order\" data-products=\"[5982,5760,5655,21038]\" class=\"wc-block-grid wp-block-handpicked-products wp-block-woocommerce-handpicked-products wc-block-handpicked-products has-4-columns has-multiple-rows\"><ul class=\"wc-block-grid__products\"><li class=\"wc-block-grid__product\"><span class=\"gtm4wp_productdata\" style=\"display:none; visibility:hidden;\" data-gtm4wp_product_data=\"{&quot;internal_id&quot;:21038,&quot;item_id&quot;:&quot;21038&quot;,&quot;item_name&quot;:&quot;6-in-1 Digital tester for soil and liquids - pH, EC, light, moisture, fertiliser and temperature&quot;,&quot;sku&quot;:&quot;PCT088&quot;,&quot;price&quot;:89.9,&quot;stocklevel&quot;:1,&quot;stockstatus&quot;:&quot;instock&quot;,&quot;google_business_vertical&quot;:&quot;retail&quot;,&quot;item_category&quot;:&quot;Producten&quot;,&quot;id&quot;:&quot;21038&quot;,&quot;productlink&quot;:&quot;https:\\\/\\\/www.plantcaretools.com\\\/en\\\/6-in-1-digital-tester-for-soil-and-liquids-ph-ec-light-moisture-fertiliser-and-temperature\\\/&quot;,&quot;item_list_name&quot;:&quot;General Product List&quot;,&quot;index&quot;:0,&quot;product_type&quot;:&quot;simple&quot;,&quot;item_list_id&quot;:&quot;general-product-list&quot;,&quot;item_brand&quot;:&quot;&quot;}\"><\/span>\n\t\t\t\t<a href=\"https:\/\/www.plantcaretools.com\/en\/6-in-1-digital-tester-for-soil-and-liquids-ph-ec-light-moisture-fertiliser-and-temperature\/\" class=\"wc-block-grid__product-link\">\n\t\t\t\t\t\n\t\t\t\t\t<div class=\"wc-block-grid__product-image\"><img loading=\"lazy\" decoding=\"async\" width=\"272\" height=\"272\" src=\"https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2024\/09\/Multi_Function_Soil_Tester_YY-1088light_ph_EC_temperature_moisture_fertility_humidity_salt_PlantCareTools11-768x768-1-272x272.webp\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Multi_Function_Soil_Tester\" srcset=\"https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2024\/09\/Multi_Function_Soil_Tester_YY-1088light_ph_EC_temperature_moisture_fertility_humidity_salt_PlantCareTools11-768x768-1-272x272.webp 272w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2024\/09\/Multi_Function_Soil_Tester_YY-1088light_ph_EC_temperature_moisture_fertility_humidity_salt_PlantCareTools11-768x768-1-300x300.webp 300w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2024\/09\/Multi_Function_Soil_Tester_YY-1088light_ph_EC_temperature_moisture_fertility_humidity_salt_PlantCareTools11-768x768-1-150x150.webp 150w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2024\/09\/Multi_Function_Soil_Tester_YY-1088light_ph_EC_temperature_moisture_fertility_humidity_salt_PlantCareTools11-768x768-1-600x600.webp 600w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2024\/09\/Multi_Function_Soil_Tester_YY-1088light_ph_EC_temperature_moisture_fertility_humidity_salt_PlantCareTools11-768x768-1-100x100.webp 100w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2024\/09\/Multi_Function_Soil_Tester_YY-1088light_ph_EC_temperature_moisture_fertility_humidity_salt_PlantCareTools11-768x768-1.webp 768w\" sizes=\"auto, (max-width: 272px) 100vw, 272px\" data-wp-pid=\"24022\" \/><\/div>\n\t\t\t\t\t<div class=\"wc-block-grid__product-title\">6-in-1 Digital tester for soil and liquids &#8211; pH, EC, light, moisture, fertiliser and temperature<\/div>\n\t\t\t\t<\/a>\n\t\t\t\t<div class=\"wc-block-grid__product-price price\"><span class=\"woocommerce-Price-amount amount\"><bdi><span class=\"woocommerce-Price-currencySymbol\" dir=\"auto\">&euro;<\/span>89,90<\/bdi><\/span><\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/li><li class=\"wc-block-grid__product\"><span class=\"gtm4wp_productdata\" style=\"display:none; visibility:hidden;\" data-gtm4wp_product_data=\"{&quot;internal_id&quot;:5655,&quot;item_id&quot;:&quot;5655&quot;,&quot;item_name&quot;:&quot;4-in-1 plant soil tester: measures pH value, humidity, temperature and light intensity&quot;,&quot;sku&quot;:&quot;PCT020&quot;,&quot;price&quot;:24.9,&quot;stocklevel&quot;:64,&quot;stockstatus&quot;:&quot;instock&quot;,&quot;google_business_vertical&quot;:&quot;retail&quot;,&quot;item_category&quot;:&quot;Measuring Instruments&quot;,&quot;id&quot;:&quot;5655&quot;,&quot;productlink&quot;:&quot;https:\\\/\\\/www.plantcaretools.com\\\/en\\\/4-in-1-soil-tester\\\/&quot;,&quot;item_list_name&quot;:&quot;General Product List&quot;,&quot;index&quot;:0,&quot;product_type&quot;:&quot;simple&quot;,&quot;item_list_id&quot;:&quot;general-product-list&quot;,&quot;item_brand&quot;:&quot;&quot;}\"><\/span>\n\t\t\t\t<a href=\"https:\/\/www.plantcaretools.com\/en\/4-in-1-soil-tester\/\" class=\"wc-block-grid__product-link\">\n\t\t\t\t\t\n\t\t\t\t\t<div class=\"wc-block-grid__product-image\"><img loading=\"lazy\" decoding=\"async\" width=\"272\" height=\"272\" src=\"https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-272x272.jpg\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"4-in-1 plant soil tester: measures pH value, humidity, temperature and light intensity\" srcset=\"https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-272x272.jpg 272w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-300x300.jpg 300w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-1024x1024.jpg 1024w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-150x150.jpg 150w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-768x768.jpg 768w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-1536x1536.jpg 1536w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-2048x2048.jpg 2048w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-600x600.jpg 600w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-100x100.jpg 100w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2017\/08\/plantcarekit_ph_temperature_moisture_light_nutrients_plantcaretools8-scaled-1200x1200.jpg 1200w\" sizes=\"auto, (max-width: 272px) 100vw, 272px\" data-wp-pid=\"20638\" \/><\/div>\n\t\t\t\t\t<div class=\"wc-block-grid__product-title\">4-in-1 plant soil tester: measures pH value, humidity, temperature and light intensity<\/div>\n\t\t\t\t<\/a>\n\t\t\t\t<div class=\"wc-block-grid__product-price price\"><span class=\"sale-price\"><del aria-hidden=\"true\"><span class=\"woocommerce-Price-amount amount\"><bdi><span class=\"woocommerce-Price-currencySymbol\" dir=\"auto\">&euro;<\/span>34,90<\/bdi><\/span><\/del> <span class=\"screen-reader-text\">Original price was: &euro;34,90.<\/span><ins aria-hidden=\"true\"><span class=\"woocommerce-Price-amount amount\"><bdi><span class=\"woocommerce-Price-currencySymbol\" dir=\"auto\">&euro;<\/span>24,90<\/bdi><\/span><\/ins><span class=\"screen-reader-text\">Current price is: &euro;24,90.<\/span><\/span><\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/li><li class=\"wc-block-grid__product\"><span class=\"gtm4wp_productdata\" style=\"display:none; visibility:hidden;\" data-gtm4wp_product_data=\"{&quot;internal_id&quot;:5982,&quot;item_id&quot;:&quot;5982&quot;,&quot;item_name&quot;:&quot;Digital Light Meter&quot;,&quot;sku&quot;:&quot;PCT190&quot;,&quot;price&quot;:22.9,&quot;stocklevel&quot;:28,&quot;stockstatus&quot;:&quot;instock&quot;,&quot;google_business_vertical&quot;:&quot;retail&quot;,&quot;item_category&quot;:&quot;Measuring Instruments&quot;,&quot;id&quot;:&quot;5982&quot;,&quot;productlink&quot;:&quot;https:\\\/\\\/www.plantcaretools.com\\\/en\\\/digital-light-meter\\\/&quot;,&quot;item_list_name&quot;:&quot;General Product List&quot;,&quot;index&quot;:0,&quot;product_type&quot;:&quot;simple&quot;,&quot;item_list_id&quot;:&quot;general-product-list&quot;,&quot;item_brand&quot;:&quot;&quot;}\"><\/span>\n\t\t\t\t<a href=\"https:\/\/www.plantcaretools.com\/en\/digital-light-meter\/\" class=\"wc-block-grid__product-link\">\n\t\t\t\t\t\n\t\t\t\t\t<div class=\"wc-block-grid__product-image\"><img loading=\"lazy\" decoding=\"async\" width=\"272\" height=\"272\" src=\"https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/06\/Digitale-lichtmeter-272x272.jpg\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Digital Light Meter - Plant Care Tools\" srcset=\"https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/06\/Digitale-lichtmeter-272x272.jpg 272w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/06\/Digitale-lichtmeter-100x100.jpg 100w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/06\/Digitale-lichtmeter-600x600.jpg 600w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/06\/Digitale-lichtmeter-300x300.jpg 300w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/06\/Digitale-lichtmeter-150x150.jpg 150w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/06\/Digitale-lichtmeter-768x768.jpg 768w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/06\/Digitale-lichtmeter.jpg 800w\" sizes=\"auto, (max-width: 272px) 100vw, 272px\" data-wp-pid=\"3388\" \/><\/div>\n\t\t\t\t\t<div class=\"wc-block-grid__product-title\">Digital Light Meter<\/div>\n\t\t\t\t<\/a>\n\t\t\t\t<div class=\"wc-block-grid__product-price price\"><span class=\"woocommerce-Price-amount amount\"><bdi><span class=\"woocommerce-Price-currencySymbol\" dir=\"auto\">&euro;<\/span>22,90<\/bdi><\/span><\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/li><li class=\"wc-block-grid__product\"><span class=\"gtm4wp_productdata\" style=\"display:none; visibility:hidden;\" data-gtm4wp_product_data=\"{&quot;internal_id&quot;:5760,&quot;item_id&quot;:&quot;5760&quot;,&quot;item_name&quot;:&quot;4 in 1 Bluetooth Plant Care Monitor&quot;,&quot;sku&quot;:&quot;PCT131&quot;,&quot;price&quot;:35.9,&quot;stocklevel&quot;:6,&quot;stockstatus&quot;:&quot;instock&quot;,&quot;google_business_vertical&quot;:&quot;retail&quot;,&quot;item_category&quot;:&quot;Measuring Instruments&quot;,&quot;id&quot;:&quot;5760&quot;,&quot;productlink&quot;:&quot;https:\\\/\\\/www.plantcaretools.com\\\/en\\\/bluetooth-plant-care-monitor\\\/&quot;,&quot;item_list_name&quot;:&quot;General Product List&quot;,&quot;index&quot;:0,&quot;product_type&quot;:&quot;simple&quot;,&quot;item_list_id&quot;:&quot;general-product-list&quot;,&quot;item_brand&quot;:&quot;&quot;}\"><\/span>\n\t\t\t\t<a href=\"https:\/\/www.plantcaretools.com\/en\/bluetooth-plant-care-monitor\/\" class=\"wc-block-grid__product-link\">\n\t\t\t\t\t\n\t\t\t\t\t<div class=\"wc-block-grid__product-image\"><img loading=\"lazy\" decoding=\"async\" width=\"272\" height=\"272\" src=\"https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-272x272.jpg\" class=\"attachment-woocommerce_thumbnail size-woocommerce_thumbnail\" alt=\"Bluetooth planten monitor - Plant Care Tools\" srcset=\"https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-272x272.jpg 272w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-100x100.jpg 100w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-600x600.jpg 600w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-300x300.jpg 300w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-1024x1024.jpg 1024w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-150x150.jpg 150w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-768x768.jpg 768w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-1536x1536.jpg 1536w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-2048x2048.jpg 2048w, https:\/\/www.plantcaretools.com\/wp-content\/uploads\/2022\/07\/MG_0355-1200x1200.jpg 1200w\" sizes=\"auto, (max-width: 272px) 100vw, 272px\" data-wp-pid=\"4418\" \/><\/div>\n\t\t\t\t\t<div class=\"wc-block-grid__product-title\">4 in 1 Bluetooth Plant Care Monitor<\/div>\n\t\t\t\t<\/a>\n\t\t\t\t<div class=\"wc-block-grid__product-price price\"><span class=\"woocommerce-Price-amount amount\"><bdi><span class=\"woocommerce-Price-currencySymbol\" dir=\"auto\">&euro;<\/span>35,90<\/bdi><\/span><\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/li><\/ul><\/div>\n\n\n<h2 class=\"wp-block-heading\">Frequently asked questions about measuring light intensity<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Lux and light requirements<\/h3>\n\n\n\n<details class=\"wp-block-details pct-kb-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>How many lux do plants need?<\/summary>\n<p class=\"wp-block-paragraph\">It depends on the plant. Low-light plants manage with 540 to 2,700 lux, medium-light plants need 2,700 to 10,800 lux and high-light plants want more than 10,800 lux (University of Minnesota). Below about 540 lux, hardly any plant survives for long.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details pct-kb-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>How much light does a monstera need?<\/summary>\n<p class=\"wp-block-paragraph\">A monstera is a medium-light plant: between 2,700 and 10,800 lux. A spot close to an east or west window therefore usually works well. Strong midday sun behind glass, however, can scorch the leaves.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details pct-kb-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>How many lux is sunlight?<\/summary>\n<p class=\"wp-block-paragraph\">Outdoors in full sun you measure more than 100,000 lux. Indoors it is much less, because glass, curtains and the distance from the window block light. A few metres from the window you often measure only a tenth of the value right next to the glass.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details pct-kb-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>How do I know if my plant gets too little or too much light?<\/summary>\n<p class=\"wp-block-paragraph\">With too little light, leaves turn pale or yellow, stems become long and thin and the leaves grow further apart. Variegated leaves may also turn completely green, and flowering plants form no buds. Too much light shows as scorched or bleached patches on the leaves (University of Minnesota).<\/p>\n<\/details>\n\n\n\n<h3 class=\"wp-block-heading\">Measuring with a phone or a light meter<\/h3>\n\n\n\n<details class=\"wp-block-details pct-kb-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>Can I use a light meter app for plants?<\/summary>\n<p class=\"wp-block-paragraph\">For a first impression, yes, but do not expect an exact number. In one test, a phone\u2019s light sensor was up to almost 40% off without calibration, and in low light (below 100 lux) even more than 60%. A separate light sensor was only 2.7% off in the same test (Gutierrez-Martinez et al., 2017). If you really want to choose a spot, use a light meter.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details pct-kb-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>What is the difference between lux and PPFD?<\/summary>\n<p class=\"wp-block-paragraph\">Lux measures how bright light looks to the human eye. PPFD, on the other hand, counts the light particles a plant uses for photosynthesis, in \u00b5mol per square metre per second. For research and growing, PPFD is therefore the better measure (Virginia Tech). To compare spots in your home in daylight, lux is fine.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details pct-kb-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>How do I convert lux to PPFD?<\/summary>\n<p class=\"wp-block-paragraph\">In daylight, divide the number of lux by 54. So 10,800 lux is roughly 200 \u00b5mol\/m\u00b2\/s. Other lamps use a different factor, for example 74 for fluorescent light (Apogee Instruments). There is no fixed factor for LED grow lights, so use the PPFD stated by the manufacturer instead.<\/p>\n<\/details>\n\n\n\n<h3 class=\"wp-block-heading\">Grow lights<\/h3>\n\n\n\n<details class=\"wp-block-details pct-kb-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>How many hours of light do plants need under a grow light?<\/summary>\n<p class=\"wp-block-paragraph\">Foliage plants need 12 to 14 hours of light a day, flowering plants 14 to 16 hours and seedlings 16 to 18 hours (University of Minnesota). Use a timer, so the plant also gets a rest every night.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details pct-kb-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>How far should a grow light be from plants?<\/summary>\n<p class=\"wp-block-paragraph\">As a guideline, hang the lamp 30 to 60 cm (12 to 24 inches) above foliage plants, 15 to 30 cm (6 to 12 inches) above flowering plants, herbs and lettuce, and 10 to 15 cm (4 to 6 inches) above seedlings (University of Minnesota). Then measure at leaf height and adjust the lamp until the value suits your plant.<\/p>\n<\/details>\n\n\n\n<p class=\"wp-block-paragraph\">Not enough light coming in? Then take a look at our <a href=\"https:\/\/www.plantcaretools.com\/en\/grow-lights-and-wifi-mood-lights\/\">grow lights<\/a>. And if you also want to know when to water, read how to <a href=\"https:\/\/www.plantcaretools.com\/en\/measure-soil-moisture-level\/\">measure soil moisture<\/a>.<\/p>\n\n\n\n<div class=\"wp-block-group pct-kb-cta is-layout-flow wp-block-group-is-layout-flow\">\n<h2 class=\"wp-block-heading\">Not sure which light meter suits you?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Send us a photo of the spot and the plant. We are happy to help you choose the right meter for free, or a grow light if the light falls short.<\/p>\n\n\n\n<div class=\"pct-kb-btns\"><a class=\"pct-kb-btn\" href=\"https:\/\/www.plantcaretools.com\/en\/measuring-instruments\/\">View measuring instruments<\/a><a class=\"pct-kb-btn alt\" href=\"https:\/\/www.plantcaretools.com\/en\/contact\/\">Ask for free advice<\/a><\/div>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">Sources<\/h3>\n\n\n\n<ul class=\"wp-block-list pct-kb-sources\">\n<li><a href=\"https:\/\/extension.umn.edu\/houseplants\/light-requirements-houseplants\" rel=\"noopener\">University of Minnesota Extension, Light requirements for houseplants<\/a>: light groups in foot-candles and PPFD<\/li>\n\n\n\n<li><a href=\"https:\/\/extension.umn.edu\/planting-and-growing-guides\/lighting-indoor-plants\" rel=\"noopener\">University of Minnesota Extension, Lighting for indoor plants<\/a>: signs of too little or too much light, hours and distance of grow lights<\/li>\n\n\n\n<li><a href=\"https:\/\/extension.msstate.edu\/publications\/care-selection-indoor-plants\" rel=\"noopener\">Mississippi State University Extension, Care and Selection of Indoor Plants<\/a>: drop in light near the window and the lower limit for plants<\/li>\n\n\n\n<li><a href=\"https:\/\/extension.illinois.edu\/houseplants\/lighting\" rel=\"noopener\">University of Illinois Extension, Houseplants: Lighting<\/a>: influence of the seasons<\/li>\n\n\n\n<li><a href=\"https:\/\/www.pubs.ext.vt.edu\/content\/dam\/pubs_ext_vt_edu\/spes\/spes-720\/SPES-720.pdf\" rel=\"noopener\">Stallknecht (2025), Calculating and Using Daily Light Integral, Virginia Cooperative Extension<\/a>: full sun and PPFD as the measure for plants<\/li>\n\n\n\n<li><a href=\"https:\/\/www.apogeeinstruments.com\/conversion-ppfd-to-lux\/\" rel=\"noopener\">Apogee Instruments, Conversion PPFD to lux<\/a>: conversion factors per light source<\/li>\n\n\n\n<li><a href=\"https:\/\/www.mdpi.com\/2076-3417\/7\/6\/616\" rel=\"noopener\">Gutierrez-Martinez et al. (2017), Smartphones as a Light Measurement Tool, Applied Sciences<\/a>: accuracy of phones<\/li>\n<\/ul>\n\n\n\n<p class=\"pct-kb-updated wp-block-paragraph\">Last updated: 27 October 2026<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Knowledge base \u00b7 Measure light intensity Measure light intensity: how many lux does your plant need? Measure light intensity at leaf height, right where your plant stands. Here you can read how many lux your plant needs, how to read a light meter and why your phone only gives a rough estimate. Updated 2026Reading time [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":13829,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_jetpack_hide_featured_image":false,"_jetpack_featured_image_duplicate_dismissed":0,"footnotes":""},"class_list":["post-10562","page","type-page","status-publish","has-post-thumbnail","hentry"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v28.4 (Yoast SEO v28.8) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Measure light intensity: how many lux do plants need?<\/title>\n<meta name=\"description\" content=\"Measure light intensity for your plants: how many lux plants need, how to read a light meter and how accurate your phone really is.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.plantcaretools.com\/en\/measure-light-intensity-plants\/\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/www.plantcaretools.com\\\/en\\\/measure-light-intensity-plants\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/www.plantcaretools.com\\\/en\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Measure light intensity for plants\"}]}]}<\/script>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"Measure light intensity: how many lux do plants need?","description":"Measure light intensity for your plants: how many lux plants need, how to read a light meter and how accurate your phone really is.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.plantcaretools.com\/en\/measure-light-intensity-plants\/","schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"BreadcrumbList","@id":"https:\/\/www.plantcaretools.com\/en\/measure-light-intensity-plants\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.plantcaretools.com\/en\/"},{"@type":"ListItem","position":2,"name":"Measure light intensity for plants"}]}]}},"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.plantcaretools.com\/en\/wp-json\/wp\/v2\/pages\/10562","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.plantcaretools.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.plantcaretools.com\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.plantcaretools.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.plantcaretools.com\/en\/wp-json\/wp\/v2\/comments?post=10562"}],"version-history":[{"count":16,"href":"https:\/\/www.plantcaretools.com\/en\/wp-json\/wp\/v2\/pages\/10562\/revisions"}],"predecessor-version":[{"id":24415,"href":"https:\/\/www.plantcaretools.com\/en\/wp-json\/wp\/v2\/pages\/10562\/revisions\/24415"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.plantcaretools.com\/en\/wp-json\/wp\/v2\/media\/13829"}],"wp:attachment":[{"href":"https:\/\/www.plantcaretools.com\/en\/wp-json\/wp\/v2\/media?parent=10562"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}