{"id":55824,"date":"2015-10-24T15:57:55","date_gmt":"2015-10-24T13:57:55","guid":{"rendered":"http:\/\/wpcalc.com\/?p=55824"},"modified":"2026-09-28T09:21:55","modified_gmt":"2026-09-28T06:21:55","slug":"heat-flux-density","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/converters\/heat-flux-density\/","title":{"rendered":"Heat Flux Density 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 Heat Flux Density Between Units<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"55824\" data-favorite-title=\"Heat Flux Density\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/converters\/heat-flux-density\/\" data-favorite-excerpt=\"Convert heat flux density between W\/m\u00b2, kW\/m\u00b2, cal\/s\u00b7cm\u00b2, BTU\/h\u00b7ft\u00b2, and BTU\/s\u00b7ft\u00b2. Enter a value, then choose the starting and target units.\" 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\/heat-flux-density\/\" method=\"POST\" class=\"calculator\" id=\"calculator-55824\" data-post=\"55824\"><fieldset class=\"fieldset-input\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field is-single\" id=\"input-1\"><label for=\"field-1\">Heat flux value<\/label><input type=\"text\" name=\"heat_flux_value\" id=\"field-1\" aria-describedby=\"calc-unit-1 calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"100\"\/><div class=\"unit\" id=\"calc-unit-1\"><\/div><small id=\"calc-info-1\">Enter the heat flux density 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=\"W\/m\u00b2\">Watt per square meter (W\/m\u00b2)<\/option><option value=\"kW\/m\u00b2\">Kilowatt per square meter (kW\/m\u00b2)<\/option><option value=\"cal\/s\u00b7cm\u00b2\">Calorie per second per square centimeter (cal\/s\u00b7cm\u00b2)<\/option><option value=\"BTU\/h\u00b7ft\u00b2\">BTU per hour per square foot (BTU\/h\u00b7ft\u00b2)<\/option><option value=\"BTU\/s\u00b7ft\u00b2\">BTU per second per square foot (BTU\/s\u00b7ft\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=\"W\/m\u00b2\">Watt per square meter (W\/m\u00b2)<\/option><option value=\"kW\/m\u00b2\">Kilowatt per square meter (kW\/m\u00b2)<\/option><option value=\"cal\/s\u00b7cm\u00b2\">Calorie per second per square centimeter (cal\/s\u00b7cm\u00b2)<\/option><option value=\"BTU\/h\u00b7ft\u00b2\">BTU per hour per square foot (BTU\/h\u00b7ft\u00b2)<\/option><option value=\"BTU\/s\u00b7ft\u00b2\">BTU per second per square foot (BTU\/s\u00b7ft\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=\"55824\">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 Heat Flux Density<\/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=\"55824\" 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>Heat Flux Density 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\\[q_{\\text{to}}=q_{\\text{from}}\\times\\frac{C_{\\text{from}}}{C_{\\text{to}}}\\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(q_{\\text{from}}\\) \u2014 the heat flux density entered in the starting unit<\/li>\n<li>\\(q_{\\text{to}}\\) \u2014 the converted heat flux density in the target unit<\/li>\n<li>\\(C_{\\text{from}}\\) and \\(C_{\\text{to}}\\) \u2014 the converter\u2019s factors for expressing each unit in W\/m\u00b2<\/li>\n<\/ul>\n<p>The calculator first expresses the entered value in W\/m\u00b2, then divides by the factor for the target unit. The result represents the same heat flux density in a different unit.<\/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>Heat Flux Density \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> convert the default value of 100 W\/m\u00b2 to kW\/m\u00b2. The converter uses factors of 1 for W\/m\u00b2 and 1,000 for kW\/m\u00b2.<\/p>\n<p>\\[100\\times\\frac{1}{1{,}000}=0.1\\ \\text{kW\/m}^2\\]<\/p>\n<p><strong>Result:<\/strong> 100 W\/m\u00b2 equals 0.1 kW\/m\u00b2.<\/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>Heat flux value<\/strong>. The number must be expressed in the unit you select next.<\/li>\n<li>Choose that unit in <strong>From unit<\/strong>. For example, select W\/m\u00b2 if your value is measured in watts per square meter.<\/li>\n<li>Choose the unit you need in <strong>To unit<\/strong>. You can select the same unit to leave the number unchanged.<\/li>\n<li>Read <strong>Converted Heat Flux Density<\/strong> for the converted number and its unit. Change either selection to compare units.<\/li>\n<\/ol>\n<p>The available units are W\/m\u00b2, kW\/m\u00b2, cal\/s\u00b7cm\u00b2, BTU\/h\u00b7ft\u00b2, and BTU\/s\u00b7ft\u00b2. Ergs per second per square centimeter are not an option in this calculator.<\/p>\n<h2>What heat flux density means<\/h2>\n<p>Heat flux density is a rate of heat transfer per unit surface area. A value of 100 W\/m\u00b2 means that heat is crossing each square meter of a surface at a rate of 100 joules per second, provided the rate is uniform over that area. It is also commonly called heat flux.<\/p>\n<p>Area matters when interpreting the number. A heat flow of 100 W across 1 m\u00b2 corresponds to an average of 100 W\/m\u00b2; the same heat flow across 2 m\u00b2 corresponds to an average of 50 W\/m\u00b2. If the heat flux varies across the surface, a single value may represent an average rather than the conditions at every point. For calculations involving total heat flow, see the <a href=\"https:\/\/wpcalc.com\/en\/converters\/heat-transfer\/\">Heat Transfer converter<\/a>.<\/p>\n<p>Heat flux density can describe heat passing through a wall, entering a solar collector, or reaching a component\u2019s surface. It is distinct from thermal conductivity: conductivity describes a material property related to heat conduction, while heat flux density describes heat transfer per area under particular conditions. Use the <a href=\"https:\/\/wpcalc.com\/en\/converters\/thermal-conductivity\/\">Thermal Conductivity converter<\/a> when you need to convert the material property instead.<\/p>\n<h2>Units and conversion factors<\/h2>\n<p>The calculator uses W\/m\u00b2 as its reference unit. Its factors state how many W\/m\u00b2 correspond to one unit of each type:<\/p>\n<ul>\n<li><strong>W\/m\u00b2:<\/strong> 1. A watt is one joule per second, so this is the SI unit for heat flux density.<\/li>\n<li><strong>kW\/m\u00b2:<\/strong> 1,000 W\/m\u00b2. This is useful when a value would otherwise require a large number of watts per square meter.<\/li>\n<li><strong>cal\/s\u00b7cm\u00b2:<\/strong> 41,868 W\/m\u00b2, using this calculator\u2019s factor.<\/li>\n<li><strong>BTU\/h\u00b7ft\u00b2:<\/strong> 3.15459 W\/m\u00b2, using this calculator\u2019s factor.<\/li>\n<li><strong>BTU\/s\u00b7ft\u00b2:<\/strong> 11,336.722 W\/m\u00b2, using this calculator\u2019s factor.<\/li>\n<\/ul>\n<p>For example, converting from kW\/m\u00b2 to W\/m\u00b2 multiplies the value by 1,000. Converting in the opposite direction divides it by 1,000. For any other pair, the formula above applies the two listed factors in sequence; you do not need to convert to W\/m\u00b2 manually.<\/p>\n<h2>Assumptions and practical limits<\/h2>\n<p>This tool converts units; it does not calculate heat flux density from temperature difference, wall thickness, material properties, or surface area. A change of units also does not establish the direction of heat flow. The <strong>Heat flux value<\/strong> field accepts nonnegative values, so enter a magnitude rather than a signed value.<\/p>\n<p>Results are rounded to eight decimal places. A very small nonzero conversion may therefore display as zero. Keep your original value and its unit when you need more precision than the displayed result provides.<\/p>\n<p>The listed BTU\/s\u00b7ft\u00b2 and BTU\/h\u00b7ft\u00b2 factors do not have the exact 3,600-to-1 ratio expected from seconds and hours alone. The calculator uses the factors shown above, so check the applicable BTU definition and conversion standard before relying on a BTU-based result for precision engineering work. Heat flux density is also different from <a href=\"https:\/\/wpcalc.com\/en\/converters\/mass-flux-density\/\">mass flux density<\/a>, which measures mass flow per unit area rather than heat transfer.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Convert heat flux density between W\/m\u00b2, kW\/m\u00b2, cal\/s\u00b7cm\u00b2, BTU\/h\u00b7ft\u00b2, and BTU\/s\u00b7ft\u00b2. Enter a value, then choose the starting and target units.<\/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-55824","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\/55824","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=55824"}],"version-history":[{"count":3,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/55824\/revisions"}],"predecessor-version":[{"id":65275,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/55824\/revisions\/65275"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=55824"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=55824"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=55824"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}