{"id":66790,"date":"2026-10-13T09:02:20","date_gmt":"2026-10-13T06:02:20","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66790"},"modified":"2026-10-13T09:02:20","modified_gmt":"2026-10-13T06:02:20","slug":"insulation-r-value-converter","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/converters\/insulation-r-value-converter\/","title":{"rendered":"Insulation R-Value 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 Insulation R-Values Between US and SI Units<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66790\" data-favorite-title=\"Insulation R-Value\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/converters\/insulation-r-value-converter\/\" data-favorite-excerpt=\"Convert insulation R-values between US imperial units (ft\u00b2\u00b7\u00b0F\u00b7h\/BTU) and SI metric units (m\u00b2\u00b7K\/W), and get the corresponding U-values in both systems. Just pick the unit system and enter the R-value.\" 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\/insulation-r-value-converter\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66790\" data-post=\"66790\"><fieldset class=\"fieldset-input is-1\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field\" id=\"input-1\"><label for=\"field-1\">Unit system of the entered R-value<\/label><div class=\"grid grid-cols-1\"><select id=\"field-1\" name=\"unit_system_of_the_entered_rvalue\"><option value=\"us\" selected>US: ft\u00b2\u00b7\u00b0F\u00b7h\/BTU<\/option><option value=\"si\">SI (metric): m\u00b2\u00b7K\/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><div class=\"field has-term\" id=\"input-2\"><label for=\"field-2\">Insulation R-value (R)<\/label><div class=\"term\">R<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"insulation_rvalue_r\" id=\"field-2\" aria-describedby=\"calc-info-2\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 13\" min=\"0\" value=\"13\"\/><small id=\"calc-info-2\">Common US values: 13 (2\u00d74 walls), 19 (2\u00d76 walls), 30\u201349 (attics)<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66790\">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> Converted Values<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>R-value (SI, metric)<\/span><span class=\"result-term\">R_SI<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"m\u00b2\u00b7K\/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 class=\"field-result\" id=\"output-2\"><span class=\"field-title\"><span>R-value (US, imperial)<\/span><span class=\"result-term\">R_US<\/span><\/span><span class=\"field-value\" id=\"result-2\" data-unit=\"ft\u00b2\u00b7\u00b0F\u00b7h\/BTU\"><\/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 class=\"field-result\" id=\"output-3\"><span class=\"field-title\"><span>U-value (SI, metric)<\/span><span class=\"result-term\">U_SI<\/span><\/span><span class=\"field-value\" id=\"result-3\" data-unit=\"W\/(m\u00b2\u00b7K)\"><\/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 class=\"field-result\" id=\"output-4\"><span class=\"field-title\"><span>U-value (US, imperial)<\/span><span class=\"result-term\">U_US<\/span><\/span><span class=\"field-value\" id=\"result-4\" data-unit=\"BTU\/(h\u00b7ft\u00b2\u00b7\u00b0F)\"><\/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=\"66790\" 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>Insulation R-Value Conversion 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\\[ R_{SI} = R_{US} \\times 0.176110 \\qquad R_{US} = \\frac{R_{SI}}{0.176110} \\]\n\\[ U = \\frac{1}{R} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(R_{US}\\) \u2014 R-value in US imperial units (ft\u00b2\u00b7\u00b0F\u00b7h\/BTU), as printed on North American product labels<\/li>\n<li>\\(R_{SI}\\) \u2014 R-value in SI metric units (m\u00b2\u00b7K\/W), used in European and international building standards<\/li>\n<li>\\(0.176110\\) \u2014 conversion factor: 1 ft\u00b2\u00b7\u00b0F\u00b7h\/BTU = 0.176110 m\u00b2\u00b7K\/W exactly (derived from 1 BTU = 1055.05585262 J)<\/li>\n<li>\\(U\\) \u2014 U-value (thermal transmittance), the reciprocal of the R-value in the same unit system<\/li>\n<\/ul>\n<p>The first two formulas convert thermal resistance between the US and SI unit systems. The third shows that the U-value is simply the inverse of the R-value: high R means strong insulation, while low U means little heat passes through.<\/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>Insulation R-Value \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> a US fiberglass batt labeled R-13 (typical for a 2\u00d74 wall) needs to be expressed in metric units for an international energy report.<\/p>\n<p>\\[ R_{SI} = 13 \\times 0.176110 = 2.289 \\ \\text{m}^2\\!\\cdot\\!\\text{K\/W} \\]<\/p>\n<p>\\[ U_{SI} = \\frac{1}{2.289} = 0.437 \\ \\text{W\/(m}^2\\!\\cdot\\!\\text{K)} \\qquad U_{US} = \\frac{1}{13} = 0.0769 \\ \\text{BTU\/(h}\\!\\cdot\\!\\text{ft}^2\\!\\cdot\\!\\text{\u00b0F)} \\]<\/p>\n<p><strong>Result:<\/strong> R-13 (US) = 2.289 m\u00b2\u00b7K\/W (SI). The matching U-values are 0.437 W\/(m\u00b2\u00b7K) in metric units and 0.0769 BTU\/(h\u00b7ft\u00b2\u00b7\u00b0F) in imperial units.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to use the calculator<\/h2>\n<ol>\n<li>In the field <strong>Unit system of the entered R-value<\/strong>, select <em>US: ft\u00b2\u00b7\u00b0F\u00b7h\/BTU<\/em> if your number comes from a North American product label, or <em>SI (metric): m\u00b2\u00b7K\/W<\/em> if it comes from a metric specification.<\/li>\n<li>Enter your value in <strong>Insulation R-value (R)<\/strong>. Decimal values such as 5.6 are accepted.<\/li>\n<li>Read the results in the <strong>Converted Values<\/strong> panel: the R-value in the other unit system, plus the U-value in both systems.<\/li>\n<\/ol>\n<h2>What is an R-value?<\/h2>\n<p>The R-value measures <strong>thermal resistance<\/strong>: how strongly a layer of material opposes the flow of heat through it. The higher the R-value, the slower the heat transfer and the better the insulation. In the US, R-values are written as plain numbers on product labels \u2014 R-13 for 2\u00d74 walls, R-19 for 2\u00d76 walls, R-30 to R-49 for attics \u2014 with the units ft\u00b2\u00b7\u00b0F\u00b7h\/BTU implied. Most of the rest of the world uses SI units, m\u00b2\u00b7K\/W, where typical whole-wall values range from about 2 to 8.<\/p>\n<p>Because the two unit systems differ by a factor of about 5.68, a US R-value and a metric R-value can look deceptively similar while describing very different performance. R-13 in US units is 2.289 m\u00b2\u00b7K\/W \u2014 not 13. Whenever you compare products, quotes, or building codes across regions, always convert first, which is exactly what this calculator does.<\/p>\n<p>The calculator also returns the <strong>U-value<\/strong>, the reciprocal of the R-value. The U-value (thermal transmittance) expresses how much heat actually passes through one square meter (or square foot) per degree of temperature difference. European building regulations and window specifications typically quote U-values: lower is better. A wall with R-13 has U = 0.0769 BTU\/(h\u00b7ft\u00b2\u00b7\u00b0F) or 0.437 W\/(m\u00b2\u00b7K).<\/p>\n<p>R-values of layers simply add up: two R-13 batts one on top of the other give R-26. U-values do not add \u2014 they combine through their reciprocals, which is why working in R-values is more convenient for assemblies.<\/p>\n<h2>Common R-values in both unit systems<\/h2>\n<table>\n<thead>\n<tr>\n<th>Application (US label)<\/th>\n<th>R (ft\u00b2\u00b7\u00b0F\u00b7h\/BTU)<\/th>\n<th>R (m\u00b2\u00b7K\/W)<\/th>\n<th>U (W\/(m\u00b2\u00b7K))<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>2\u00d74 wall cavity<\/td>\n<td>13<\/td>\n<td>2.29<\/td>\n<td>0.437<\/td>\n<\/tr>\n<tr>\n<td>2\u00d76 wall cavity<\/td>\n<td>19<\/td>\n<td>3.35<\/td>\n<td>0.299<\/td>\n<\/tr>\n<tr>\n<td>Attic \/ ceiling (minimum)<\/td>\n<td>30<\/td>\n<td>5.28<\/td>\n<td>0.189<\/td>\n<\/tr>\n<tr>\n<td>Attic \/ ceiling (cold climates)<\/td>\n<td>38<\/td>\n<td>6.69<\/td>\n<td>0.149<\/td>\n<\/tr>\n<tr>\n<td>High-performance attic<\/td>\n<td>49<\/td>\n<td>8.63<\/td>\n<td>0.116<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Limitations and practical tips<\/h2>\n<ul>\n<li><strong>Nominal vs. whole-assembly R.<\/strong> Label R-values describe the insulation material alone. Real walls lose performance to studs, fasteners, and gaps (thermal bridging), so a 2\u00d74 wall with R-13 batts may perform closer to R-9 to R-11 overall.<\/li>\n<li><strong>R-value is not everything.<\/strong> It only covers conductive heat flow at steady state. Air leakage, moisture, thermal mass, and radiant gain can matter as much as, or more than, the R-value \u2014 an airtight R-13 wall often outperforms a leaky R-19 one.<\/li>\n<li><strong>Conditions matter.<\/strong> Laboratory R-values are measured at a standard mean temperature (about 24 \u00b0C \/ 75 \u00b0F). Some materials, particularly loose-fill and foams, lose or gain resistance at temperature extremes or as they age and settle.<\/li>\n<li><strong>Mind the U-value direction.<\/strong> When reading U-values, remember that lower is better \u2014 the opposite of R-values. If a specification quotes a U-value, this calculator's reciprocal outputs let you cross-check it.<\/li>\n<li><strong>Units are not optional.<\/strong> A bare \"R-5\" in a European document almost certainly means 5 m\u00b2\u00b7K\/W (\u2248 R-28 US), not 5 ft\u00b2\u00b7\u00b0F\u00b7h\/BTU. Always confirm the unit system before comparing.<\/li>\n<\/ul>\n<p>If you work with thermal and climate calculations, you may also find our <a href=\"https:\/\/wpcalc.com\/en\/converters\/heat-index-calculator\/\">Heat Index Calculator<\/a>, <a href=\"https:\/\/wpcalc.com\/en\/converters\/dew-point-calculator\/\">Dew Point Calculator<\/a>, and <a href=\"https:\/\/wpcalc.com\/en\/converters\/wind-chill-calculator\/\">Wind Chill Calculator<\/a> useful for related HVAC and weather analysis.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Convert insulation R-values between US imperial units (ft\u00b2\u00b7\u00b0F\u00b7h\/BTU) and SI metric units (m\u00b2\u00b7K\/W), and get the corresponding U-values in both systems. Just pick the unit system and enter the R-value.<\/p>\n","protected":false},"author":3168,"featured_media":0,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[3],"tags":[34],"class_list":["post-66790","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\/66790","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\/3168"}],"replies":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/comments?post=66790"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66790\/revisions"}],"predecessor-version":[{"id":66791,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66790\/revisions\/66791"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66790"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66790"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66790"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}