{"id":55842,"date":"2015-10-24T16:00:02","date_gmt":"2015-10-24T14:00:02","guid":{"rendered":"http:\/\/wpcalc.com\/?p=55842"},"modified":"2026-09-28T09:25:16","modified_gmt":"2026-09-28T06:25:16","slug":"light-illumination","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/converters\/light-illumination\/","title":{"rendered":"Light Illumination Converter"},"content":{"rendered":"<section class=\"not-prose calculator-box\" aria-labelledby=\"calculator-title\"><div class=\"flex items-baseline sm:items-center justify-between gap-2 sm:gap-3\"><div class=\"flex flex-col sm:flex-row sm:items-center gap-2\"><span class=\"icon icon-calculator text-primary-700! text-base! dark:text-primary-300!\" aria-hidden=\"true\"><\/span><h2 id=\"calculator-title\" class=\"text-lg font-display font-bold\">Convert Light Illumination Between Units<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"55842\" data-favorite-title=\"Light Illumination\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/converters\/light-illumination\/\" data-favorite-excerpt=\"Convert light levels between lux, foot-candles, phot, and lumen-based units. Enter an Illumination value, then choose the From unit and To unit.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-physic\">\n    <span class=\"icon icon-shape-star-empty\" aria-hidden=\"true\"><\/span>\n  <\/button>\n  <div class=\"calcdash-favorite__tip\" aria-hidden=\"true\">\n   <span class=\"favorite-tooltip\" id=\"favorite-tooltip\"><\/span>\n  <\/div>\n  <span class=\"sr-only\" role=\"status\" id=\"favorite-status\"><\/span>\n<\/div><\/div><form action=\"https:\/\/wpcalc.com\/en\/converters\/light-illumination\/\" method=\"POST\" class=\"calculator\" id=\"calculator-55842\" data-post=\"55842\"><fieldset class=\"fieldset-input\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field is-single\" id=\"input-1\"><label for=\"field-1\">Illumination value<\/label><input type=\"text\" name=\"illumination_value\" id=\"field-1\" aria-describedby=\"calc-unit-1 calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"500\"\/><div class=\"unit\" id=\"calc-unit-1\"><\/div><small id=\"calc-info-1\">Enter the illumination (light level) value to convert<\/small><\/div><div class=\"field\" id=\"input-2\"><label for=\"field-2\">From unit<\/label><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"from_unit\"><option value=\"lx\">Lux (lx)<\/option><option value=\"ph\">Phot (ph)<\/option><option value=\"fc\">Foot-candle (fc)<\/option><option value=\"lm\/m\u00b2\">Lumen\/m\u00b2 (lm\/m\u00b2)<\/option><option value=\"lm\/cm\u00b2\">Lumen\/cm\u00b2 (lm\/cm\u00b2)<\/option><option value=\"cd\/m\u00b2\">Candela\/m\u00b2 (cd\/m\u00b2)<\/option><\/select><svg class=\"pointer-events-none col-start-1 row-start-1 mr-2 size-5 self-center justify-self-end text-gray-500 sm:size-4\" viewBox=\"0 0 16 16\" fill=\"currentColor\" aria-hidden=\"true\" data-slot=\"icon\">\n              <path fill-rule=\"evenodd\" d=\"M4.22 6.22a.75.75 0 0 1 1.06 0L8 8.94l2.72-2.72a.75.75 0 1 1 1.06 1.06l-3.25 3.25a.75.75 0 0 1-1.06 0L4.22 7.28a.75.75 0 0 1 0-1.06Z\" clip-rule=\"evenodd\" \/>\n            <\/svg><\/div><\/div><div class=\"field\" id=\"input-3\"><label for=\"field-3\">To unit<\/label><div class=\"grid grid-cols-1\"><select id=\"field-3\" name=\"to_unit\"><option value=\"lx\">Lux (lx)<\/option><option value=\"ph\">Phot (ph)<\/option><option value=\"fc\">Foot-candle (fc)<\/option><option value=\"lm\/m\u00b2\">Lumen\/m\u00b2 (lm\/m\u00b2)<\/option><option value=\"lm\/cm\u00b2\">Lumen\/cm\u00b2 (lm\/cm\u00b2)<\/option><option value=\"cd\/m\u00b2\">Candela\/m\u00b2 (cd\/m\u00b2)<\/option><\/select><svg class=\"pointer-events-none col-start-1 row-start-1 mr-2 size-5 self-center justify-self-end text-gray-500 sm:size-4\" viewBox=\"0 0 16 16\" fill=\"currentColor\" aria-hidden=\"true\" data-slot=\"icon\">\n              <path fill-rule=\"evenodd\" d=\"M4.22 6.22a.75.75 0 0 1 1.06 0L8 8.94l2.72-2.72a.75.75 0 1 1 1.06 1.06l-3.25 3.25a.75.75 0 0 1-1.06 0L4.22 7.28a.75.75 0 0 1 0-1.06Z\" clip-rule=\"evenodd\" \/>\n            <\/svg><\/div><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"55842\">Calculate<\/button><button type=\"reset\">Reset<\/button><\/div><div class=\"field is-checkbox hidden!\" id=\"field-auto-calc\"><input type=\"checkbox\" id=\"auto-calc\"><label for=\"auto-calc\">Calculate automatically<\/label><small>If enabled, the result will update automatically when you change any value.<\/small><\/div><div class=\"fieldset-result is-hidden\" aria-labelledby=\"result-title\" aria-live=\"polite\" role=\"region\"> <h3 class=\"result-title bg-gradient-to-r from-primary-50 to-gray-50 dark:from-primary-900 dark:to-gray-800\" id=\"result-title\"><span class=\"icon icon-s-pulse\" aria-hidden=\"true\"><\/span> Your Results<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Converted Illumination<\/span><\/span><span class=\"field-value\" id=\"result-1\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><\/div><div class=\"result-actions\"><button type=\"button\" class=\"copy-link\"><svg viewBox=\"0 0 20 20\" fill=\"currentColor\" aria-hidden=\"true\"><path d=\"M12.232 4.232a2.5 2.5 0 0 1 3.536 3.536l-1.225 1.224a.75.75 0 0 0 1.061 1.06l1.224-1.224a4 4 0 0 0-5.656-5.656l-3 3a4 4 0 0 0 .225 5.865.75.75 0 0 0 .977-1.138 2.5 2.5 0 0 1-.142-3.667l3-3Z\"\/><path d=\"M11.603 7.963a.75.75 0 0 0-.977 1.138 2.5 2.5 0 0 1 .142 3.667l-3 3a2.5 2.5 0 0 1-3.536-3.536l1.225-1.224a.75.75 0 0 0-1.061-1.06l-1.224 1.224a4 4 0 1 0 5.656 5.656l3-3a4 4 0 0 0-.225-5.865Z\"\/><\/svg><span class=\"copy-link__text\">Copy link to this calculation<\/span><\/button><span class=\"sr-only\" role=\"status\" id=\"copy-link-status\"><\/span><\/div><\/div><a href=\"#respond\" class=\"hidden transition-opacity duration-300 opacity-0 w-50 text-sm justify-center items-center gap-2 px-4 py-2 rounded bg-gray-200 text-gray-700 hover:bg-gray-300\" id=\"leave-comment\"><span class=\"icon icon-comments\" aria-hidden=\"true\"><\/span>Leave a Comment<\/a><\/form><\/section><section id=\"calc-reactions\" class=\"not-prose hidden my-12 bg-gradient-to-r from-primary-50 to-gray-50 border border-indigo-100 rounded-xl px-6 py-4 shadow-sm\" data-post=\"55842\" aria-live=\"polite\" aria-labelledby=\"calc-reactions-title\"><p id=\"calc-reactions-title\" class=\"text-sm text-gray-500 text-center mb-2\">How did this result make you feel?<\/p><div role=\"group\" aria-labelledby=\"calc-reactions-title\" class=\"grid grid-cols-3 sm:flex sm:flex-row sm:justify-around gap-4 sm:items-center sm:flex-wrap\"><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"like\"><span class=\"reaction-count\" data-reaction-count=\"like\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude00 <\/span><span class=\"reaction-description font-medium\">Like <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"helpful\"><span class=\"reaction-count\" data-reaction-count=\"helpful\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\udca1 <\/span><span class=\"reaction-description font-medium\">Helpful <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"confused\"><span class=\"reaction-count\" data-reaction-count=\"confused\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude15 <\/span><span class=\"reaction-description font-medium\">Confused <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"disappointed\"><span class=\"reaction-count\" data-reaction-count=\"disappointed\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude1e <\/span><span class=\"reaction-description font-medium\">Disappointed <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"inaccurate\"><span class=\"reaction-count\" data-reaction-count=\"inaccurate\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\u274c <\/span><span class=\"reaction-description font-medium\">Inaccurate <\/span><\/button><\/div><div id=\"reaction-message\" class=\"hidden mt-8 rounded-md border border-primary-100 bg-white\/50 backdrop-blur-sm px-4 py-2 text-sm text-center shadow-sm\"><\/div><\/section><div class=\"calcdash-ad not-prose calcdash-ad--calc_result calcdash-ad--in-article\"><ins class=\"adsbygoogle\" style=\"display:block\" data-ad-client=\"ca-pub-1721569815777345\" data-ad-slot=\"6317458308\" data-ad-layout=\"in-article\" data-ad-format=\"fluid\"><\/ins><script>(adsbygoogle = window.adsbygoogle || []).push({});<\/script><\/div>\n<style id=\"wpcoderpro-inline-1\">.formula-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section class=\"formula-box\" aria-labelledby=\"formula-title\">\r\n\t<div id=\"formula-title\" class=\"not-prose font-display mb-4\"><span class=\"icon icon-formula\" aria-hidden=\"true\"><\/span><h2>Light Illumination Formula<\/h2><\/div>\r\n\t<figure class=\"not-prose formula\">\r\n\t\t<figcaption class=\"formula-title\">Formula<\/figcaption>\r\n\t\t<div class=\"text-base text-gray-800\" id=\"formula\">\n\\[E_{\\mathrm{to}}=E_{\\mathrm{from}}\\times\\frac{f_{\\mathrm{from}}}{f_{\\mathrm{to}}}\\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(E_{\\mathrm{from}}\\) \u2014 the entered illumination value.<\/li>\n<li>\\(E_{\\mathrm{to}}\\) \u2014 the converted value.<\/li>\n<li>\\(f_{\\mathrm{from}}\\) and \\(f_{\\mathrm{to}}\\) \u2014 the selected units\u2019 factors relative to lux.<\/li>\n<\/ul>\n<p>The converter first expresses the entered value in lux, then divides by the factor for the destination unit. This formula applies to the illuminance units listed below; the candela-per-square-meter option has an important limitation explained later.<\/p>\n<p>\r\n<\/section>\n<style id=\"wpcoderpro-inline-459\">.calculation-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section id=\"calculation\" class=\"calculation-box\" aria-labelledby=\"calculation-title\">\r\n\t<div id=\"calculation-title\" class=\"not-prose font-display\"><span class=\"icon icon-unordered-list\" aria-hidden=\"true\"><\/span><h2>Light Illumination \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> convert the default value of 500 lux to foot-candles. The calculator uses 10.76391 lux per foot-candle.<\/p>\n<p>\\[500\\times\\frac{1}{10.76391}=46.451522\\ \\mathrm{fc}\\]<\/p>\n<p><strong>Result:<\/strong> 500 lx is approximately 46.451522 fc.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to use the calculator<\/h2>\n<ol>\n<li>Enter a nonnegative number in <strong>Illumination value<\/strong>. Use the light level measured or specified for the surface of interest.<\/li>\n<li>Choose the unit of that number under <strong>From unit<\/strong>. The default is Lux (lx).<\/li>\n<li>Choose the unit you need under <strong>To unit<\/strong>. The default is Foot-candle (fc).<\/li>\n<li>Read <strong>Converted Illumination<\/strong>. The result includes the selected destination unit and is rounded to six decimal places.<\/li>\n<\/ol>\n<p>For example, leave the defaults unchanged to reproduce the calculation above. You can also select the same unit in both menus to leave the numerical value unchanged. Check the unit beside any value you copy into a lighting plan or measurement record.<\/p>\n<h2>What illuminance measures<\/h2>\n<p>Illuminance describes the luminous flux arriving at a surface per unit area. Its SI unit is the lux: one lux equals one lumen per square meter. A surface receiving 500 lumens spread uniformly over one square meter therefore has an average illuminance of 500 lx. The measurement describes light <em>falling on<\/em> the surface, not the total light produced by a lamp or how bright the surface appears to an observer.<\/p>\n<p>Unit conversion helps when a light meter, design document, or lighting recommendation uses a different system. Foot-candles are common in some US lighting work; one foot-candle is one lumen per square foot, approximately 10.76391 lx. Phot is a metric CGS unit equal to 10,000 lx. The menu\u2019s Lumen\/m\u00b2 option is numerically identical to lux, while one lumen per square centimeter equals 10,000 lx.<\/p>\n<p>A converted value represents the same stated illuminance, not a change in the lighting. If a plan calls for a value in foot-candles but a meter reports lux, conversion puts the figures on a comparable scale. It does not establish whether the measured level meets a particular task requirement: that also depends on where the reading was taken, the applicable guidance, and the conditions during measurement.<\/p>\n<h2>Units, assumptions, and practical limits<\/h2>\n<ul>\n<li><strong>Lux (lx) and lumen\/m\u00b2:<\/strong> factor 1; these are two ways to express the same illuminance unit.<\/li>\n<li><strong>Foot-candle (fc):<\/strong> factor 10.76391 lx per fc, as used by this calculator.<\/li>\n<li><strong>Phot (ph) and lumen\/cm\u00b2:<\/strong> factor 10,000 lx per unit.<\/li>\n<li><strong>Candela\/m\u00b2 (cd\/m\u00b2):<\/strong> a unit of <em>luminance<\/em>, not illuminance. Its inclusion in the menu does not make it directly convertible to lux.<\/li>\n<\/ul>\n<p>When cd\/m\u00b2 is selected, this calculator assigns it a factor of 1, so it displays the same number when converting between cd\/m\u00b2 and lux. Treat that output as a numerical placeholder, <strong>not a physical conversion<\/strong>. Luminance describes light emitted or reflected in a particular direction per unit projected area; illuminance describes light arriving at a surface. Relating the two requires additional information about the surface and lighting geometry. For luminance units, use the <a href=\"https:\/\/wpcalc.com\/en\/converters\/light-luminance\/\">Light Luminance converter<\/a> instead.<\/p>\n<p>Real readings can vary across a desk, floor, or wall. Measure at the relevant surface and position, and record the conditions if you need to compare readings later. This converter changes units only: it cannot account for distance from a light source, beam spread, shadows, or reflectance. Likewise, lamp output in lumens does not by itself determine illuminance at a surface. To examine related quantities separately, see the <a href=\"https:\/\/wpcalc.com\/en\/converters\/luminous-intensity\/\">Luminous Intensity converter<\/a> or the <a href=\"https:\/\/wpcalc.com\/en\/converters\/lumens-to-watts\/\">Lumens to Watts calculator<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Convert light levels between lux, foot-candles, phot, and lumen-based units. Enter an Illumination value, then choose the From unit and To unit.<\/p>\n","protected":false},"author":70,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[3],"tags":[34],"class_list":["post-55842","post","type-post","status-publish","format-standard","hentry","category-converters","tag-physics-units"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/55842","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/users\/70"}],"replies":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/comments?post=55842"}],"version-history":[{"count":2,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/55842\/revisions"}],"predecessor-version":[{"id":65283,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/55842\/revisions\/65283"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=55842"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=55842"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=55842"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}