{"id":55834,"date":"2015-10-24T16:00:13","date_gmt":"2015-10-24T14:00:13","guid":{"rendered":"http:\/\/wpcalc.com\/?p=55834"},"modified":"2026-09-28T09:26:50","modified_gmt":"2026-09-28T06:26:50","slug":"lumens-to-watts","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/converters\/lumens-to-watts\/","title":{"rendered":"Lumens to Watts 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 Lumens to Watts Based on Luminous Efficacy<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"55834\" data-favorite-title=\"Lumens to Watts\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/converters\/lumens-to-watts\/\" data-favorite-excerpt=\"Estimate a light source\u2019s power consumption from its brightness in lumens. Enter the luminous flux and select a luminous efficacy to convert lumens to watts.\" 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\/lumens-to-watts\/\" method=\"POST\" class=\"calculator\" id=\"calculator-55834\" data-post=\"55834\"><fieldset class=\"fieldset-input\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Luminous flux<\/label><div class=\"term\">L<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"luminous_flux\" id=\"field-1\" aria-describedby=\"calc-unit-1 calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"800\"\/><div class=\"unit\" id=\"calc-unit-1\">lm<\/div><small id=\"calc-info-1\">Enter the luminous flux (lumens)<\/small><\/div><div class=\"field\" id=\"input-2\"><label for=\"field-2\">Luminous efficacy<\/label><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"luminous_efficacy\"><option value=\"10\">Incandescent bulb (10 lm\/W)<\/option><option value=\"15\">Halogen bulb (15 lm\/W)<\/option><option value=\"60\">Fluorescent lamp (60 lm\/W)<\/option><option value=\"90\">LED (90 lm\/W)<\/option><option value=\"120\">Efficient LED (120 lm\/W)<\/option><option value=\"683\">Theoretical max (683 lm\/W)<\/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=\"55834\">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>Power consumption<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"W\"><\/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=\"55834\" 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>Lumens to Watts 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\\[ P = \\frac{L}{E} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(P\\) \u2014 estimated electrical power consumption (W)<\/li>\n<li>\\(L\\) \u2014 luminous flux, or total visible light output (lm)<\/li>\n<li>\\(E\\) \u2014 luminous efficacy of the light source (lm\/W)<\/li>\n<\/ul>\n<p>Divide the light output by the number of lumens produced per watt to estimate the electrical power needed. The result depends on the efficacy you select, not on lumens alone.<\/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>Lumens to Watts \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> an LED produces 800 lumens and has a luminous efficacy of 90 lumens per watt, the calculator\u2019s default values.<\/p>\n<p>\\[ P = \\frac{800\\ \\mathrm{lm}}{90\\ \\mathrm{lm\/W}} = 8.888\\ldots\\ \\mathrm{W} \\approx 8.8889\\ \\mathrm{W} \\]<\/p>\n<p><strong>Result:<\/strong> the estimated power consumption is 8.8889 W.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to use the calculator<\/h2>\n<ol>\n<li>Enter the light source\u2019s rated output in <strong>Luminous flux<\/strong>, measured in lumens (lm). For a replacement bulb, use the lumens printed on its packaging rather than the wattage of the old bulb.<\/li>\n<li>Choose a value under <strong>Luminous efficacy<\/strong>. The menu provides representative values for incandescent, halogen, fluorescent and LED lamps, plus a theoretical maximum.<\/li>\n<li>Read <strong>Power consumption<\/strong> in watts (W). The calculator divides your entered lumens by the selected efficacy and displays the result to four decimal places.<\/li>\n<\/ol>\n<p>If you know the lamp\u2019s actual efficacy from a product specification, use it to assess how closely one of the available choices represents that lamp. The calculator does not offer a field for entering a custom efficacy.<\/p>\n<h2>What lumens to watts means<\/h2>\n<p>Lumens measure <strong>luminous flux<\/strong>: the total amount of visible light emitted by a source, weighted for human vision. Watts measure electrical power consumed. They describe different things, so there is no single conversion factor that works for every lamp. A more efficient source can produce the same number of lumens while drawing fewer watts.<\/p>\n<p><strong>Luminous efficacy<\/strong> connects the two measurements. It is the lamp\u2019s lumen output divided by its electrical power input, expressed in lm\/W. For example, an 800 lm source rated at 80 lm\/W would use an estimated 10 W, while one rated at 100 lm\/W would use 8 W. A higher efficacy means less power is required for the same light output.<\/p>\n<p>The result helps you compare lamps with similar lumen ratings and estimate their electricity use. It does not say how bright a surface will be: that also depends on distance, beam direction and the surrounding space. For measurements of light arriving at a surface, see the <a href=\"https:\/\/wpcalc.com\/en\/converters\/light-illumination\/\">Light Illumination converter<\/a>. To compare light emitted in a particular direction, see the <a href=\"https:\/\/wpcalc.com\/en\/converters\/luminous-intensity\/\">Luminous Intensity converter<\/a>.<\/p>\n<h2>Example estimates for an 800-lumen lamp<\/h2>\n<p>These values use the exact efficacy choices in the calculator. They illustrate why a lumen rating alone cannot determine wattage.<\/p>\n<table>\n<thead>\n<tr>\n<th>Luminous efficacy choice<\/th>\n<th>Efficacy<\/th>\n<th>Estimated power<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Incandescent bulb<\/td>\n<td>10 lm\/W<\/td>\n<td>80 W<\/td>\n<\/tr>\n<tr>\n<td>Halogen bulb<\/td>\n<td>15 lm\/W<\/td>\n<td>53.3333 W<\/td>\n<\/tr>\n<tr>\n<td>Fluorescent lamp<\/td>\n<td>60 lm\/W<\/td>\n<td>13.3333 W<\/td>\n<\/tr>\n<tr>\n<td>LED<\/td>\n<td>90 lm\/W<\/td>\n<td>8.8889 W<\/td>\n<\/tr>\n<tr>\n<td>Efficient LED<\/td>\n<td>120 lm\/W<\/td>\n<td>6.6667 W<\/td>\n<\/tr>\n<tr>\n<td>Theoretical max<\/td>\n<td>683 lm\/W<\/td>\n<td>1.1713 W<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Assumptions and practical limits<\/h2>\n<p>The selectable efficacies are representative figures, not guarantees for every product in a category. Actual performance varies with lamp design, light color, operating conditions and age. For a purchase or energy-cost estimate, check the specific product\u2019s rated lumens and input watts; those figures are more reliable than a category-wide estimate.<\/p>\n<p>Use efficacy based on <strong>electrical power drawn by the complete lamp<\/strong> when you want its input wattage. An LED chip\u2019s efficacy may differ from that of the finished bulb because the driver and other components consume power or reduce the light that leaves the lamp. A fixture can reduce delivered light further. The calculation also assumes the selected efficacy applies at the brightness level you entered; dimming may change a lamp\u2019s efficacy.<\/p>\n<p>The 683 lm\/W option represents an ideal photopic limit for monochromatic light near the wavelength of peak human visual sensitivity. It is not a realistic efficacy estimate for an ordinary white lamp. Select a lamp category instead when estimating household or workplace lighting power.<\/p>\n<p>To estimate energy use after finding wattage, multiply watts by operating hours and divide by 1,000 to get kilowatt-hours (kWh). For example, an estimated 8.8889 W lamp running for 1,000 hours uses about 8.89 kWh. This is an energy estimate, not an electricity cost; cost also depends on your price per kWh.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Estimate a light source\u2019s power consumption from its brightness in lumens. Enter the luminous flux and select a luminous efficacy to convert lumens to watts.<\/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-55834","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\/55834","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=55834"}],"version-history":[{"count":3,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/55834\/revisions"}],"predecessor-version":[{"id":65287,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/55834\/revisions\/65287"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=55834"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=55834"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=55834"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}