{"id":67405,"date":"2026-10-21T10:19:12","date_gmt":"2026-10-21T07:19:12","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=67405"},"modified":"2026-10-21T10:19:12","modified_gmt":"2026-10-21T07:19:12","slug":"insulation-calculator-r-value-and-rolls","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/life\/insulation-calculator-r-value-and-rolls\/","title":{"rendered":"Insulation Calculator \u2013 R-Value and Rolls"},"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\">Estimate Insulation Thickness, Rolls and Cost<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"67405\" data-favorite-title=\"Insulation\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/life\/insulation-calculator-r-value-and-rolls\/\" data-favorite-excerpt=\"Estimate how much insulation you need: enter your project, climate zone, area and material to get the target R-value, required thickness in inches or mm, number of rolls, bags or kits, and the material cost.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-eco-home\">\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\/life\/insulation-calculator-r-value-and-rolls\/\" method=\"POST\" class=\"calculator\" id=\"calculator-67405\" data-post=\"67405\"><fieldset class=\"fieldset-input is-2\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"is-single field\" id=\"input-1\"><span class=\"font-semibold\">Insulation setup<\/span><\/div><div class=\"field is-single\" id=\"input-2\"><label for=\"field-2\">Project<\/label><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"project\"><option value=\"attic\" selected>Attic \/ ceiling (over joists)<\/option><option value=\"wall\">Exterior wall (between studs)<\/option><option value=\"floor\">Floor over unconditioned space<\/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 is-single\" id=\"input-3\"><label for=\"field-3\">DOE climate zone<\/label><div class=\"grid grid-cols-1\"><select id=\"field-3\" name=\"doe_climate_zone\"><option value=\"z1\">Zone 1 (Miami, Honolulu)<\/option><option value=\"z2\">Zone 2 (Houston, Phoenix)<\/option><option value=\"z3\">Zone 3 (Atlanta, Dallas, Los Angeles)<\/option><option value=\"z4\" selected>Zone 4 (Kansas City, Seattle, Baltimore)<\/option><option value=\"z5\">Zone 5 (Chicago, Denver, New York)<\/option><option value=\"z6\">Zone 6 (Minneapolis, Helena)<\/option><option value=\"z7\">Zone 7 (Fargo, Duluth)<\/option><option value=\"z8\">Zone 8 (Fairbanks)<\/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 is-single\" id=\"input-4\"><label for=\"field-4\">Target R-value<\/label><div class=\"grid grid-cols-1\"><select id=\"field-4\" name=\"target_rvalue\"><option value=\"doe\" selected>Use the DOE recommendation for this project and zone<\/option><option value=\"custom\">Custom R-value<\/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-5\" hidden><label for=\"field-5\">Custom R-value<\/label><input type=\"text\" name=\"custom_rvalue\" id=\"field-5\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"1\" max=\"100\" value=\"49\"\/><\/div><div class=\"field is-single\" id=\"input-6\"><label for=\"field-6\">Insulation type<\/label><div class=\"grid grid-cols-1\"><select id=\"field-6\" name=\"insulation_type\"><option value=\"batt\" selected>Fiberglass batts \/ rolls \u2014 about R-3.1 per inch<\/option><option value=\"blownfg\">Blown-in fiberglass \u2014 about R-2.5 per inch<\/option><option value=\"blowncell\">Blown-in cellulose \u2014 about R-3.5 per inch<\/option><option value=\"opencell\">Spray foam, open-cell \u2014 about R-3.6 per inch<\/option><option value=\"closedcell\">Spray foam, closed-cell \u2014 about R-6.5 per inch<\/option><option value=\"custom\">Custom material \u2014 set R per inch<\/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-7\" hidden><label for=\"field-7\">Custom R per inch<\/label><input type=\"text\" name=\"custom_r_per_inch\" id=\"field-7\" aria-describedby=\"calc-info-7\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0.1\" max=\"20\" value=\"3.1\"\/><small id=\"calc-info-7\">Type the R-value per inch of your actual product.<\/small><\/div><div class=\"field is-single\" id=\"input-8\"><label for=\"field-8\">Stud \/ joist spacing<\/label><div class=\"grid grid-cols-1\"><select id=\"field-8\" name=\"stud_joist_spacing\"><option value=\"s16\" selected>16 in on center<\/option><option value=\"s24\">24 in on center<\/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=\"is-single field\" id=\"input-9\"><span class=\"font-semibold\">Area to insulate<\/span><\/div><div class=\"field is-single\" id=\"input-10\"><label for=\"field-10\">Area method<\/label><div class=\"grid grid-cols-1\"><select id=\"field-10\" name=\"area_method\"><option value=\"rect\" selected>Rectangle (length \u00d7 width)<\/option><option value=\"total\">Total area (known)<\/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-11\"><label for=\"field-11\">Length<\/label><div class=\"field-group\"><input type=\"text\" name=\"length\" id=\"field-11\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"40\"\/><div class=\"grid grid-cols-1\"><select id=\"field-12\" name=\"unit\" aria-label=\"Unit\"><option value=\"ft\" selected>ft<\/option><option value=\"in\">in<\/option><option value=\"m\">m<\/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><div class=\"field\" id=\"input-12\"><label for=\"field-13\">Width<\/label><div class=\"field-group\"><input type=\"text\" name=\"width\" id=\"field-13\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"30\"\/><div class=\"grid grid-cols-1\"><select id=\"field-14\" name=\"unit\" aria-label=\"Unit\"><option value=\"ft\" selected>ft<\/option><option value=\"in\">in<\/option><option value=\"m\">m<\/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><div class=\"field\" id=\"input-13\" hidden><label for=\"field-15\">Total area<\/label><div class=\"field-group\"><input type=\"text\" name=\"total_area\" id=\"field-15\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"1200\"\/><div class=\"grid grid-cols-1\"><select id=\"field-16\" name=\"area_unit\" aria-label=\"Area unit\"><option value=\"sqft\" selected>sq ft<\/option><option value=\"sqyd\">sq yd<\/option><option value=\"sqm\">sq m<\/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><div class=\"field\" id=\"input-14\"><label for=\"field-17\">Windows &amp; doors to subtract<\/label><div class=\"field-group\"><input type=\"text\" name=\"windows_doors_to_subtract\" id=\"field-17\" aria-describedby=\"calc-info-17\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"0\"\/><div class=\"grid grid-cols-1\"><select id=\"field-18\" name=\"area_unit\" aria-label=\"Area unit\"><option value=\"sqft\" selected>sq ft<\/option><option value=\"sqyd\">sq yd<\/option><option value=\"sqm\">sq m<\/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><small id=\"calc-info-17\">Total opening area you will not insulate; leave 0 if none.<\/small><\/div><div class=\"field\" id=\"input-15\"><label for=\"field-19\">Coverage per package<\/label><div class=\"field-group\"><input type=\"text\" name=\"coverage_per_package\" id=\"field-19\" aria-describedby=\"calc-info-19\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"80\"\/><div class=\"grid grid-cols-1\"><select id=\"field-20\" name=\"sold_as\" aria-label=\"Sold as\"><option value=\"sqft\" selected>ft\u00b2 per package<\/option><option value=\"bf\">board ft per kit<\/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><small id=\"calc-info-19\">Batts, rolls and blown-in: ft\u00b2 covered by one package at the installed thickness. Spray foam kits: board feet (1 board ft = 1 ft\u00b2, 1 in thick).<\/small><\/div><div class=\"field\" id=\"input-16\"><label for=\"field-21\">Waste allowance<\/label><input type=\"text\" name=\"waste_allowance\" id=\"field-21\" aria-describedby=\"calc-unit-21 calc-info-21\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" max=\"100\" value=\"10\"\/><div class=\"unit\" id=\"calc-unit-21\">%<\/div><small id=\"calc-info-21\">Covers cuts, compression and settling; 5\u201310% is typical.<\/small><\/div><div class=\"field\" id=\"input-17\"><label for=\"field-22\">Price<\/label><div class=\"field-group\"><input type=\"text\" name=\"price\" id=\"field-22\" aria-describedby=\"calc-info-22\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"50\"\/><div class=\"grid grid-cols-1\"><select id=\"field-23\" name=\"price_basis\" aria-label=\"Price basis\"><option value=\"package\" selected>$ per package<\/option><option value=\"sqft\">$ per ft\u00b2<\/option><option value=\"bf\">$ per board ft<\/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><small id=\"calc-info-22\">Optional \u2014 clear this field to omit the cost estimate.<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"67405\">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> Insulation Estimate<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Net area to insulate<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"ft\u00b2\"><\/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>Net area to insulate<\/span><\/span><span class=\"field-value\" id=\"result-2\" data-unit=\"m\u00b2\"><\/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>Target R-value<\/span><\/span><span class=\"field-value\" id=\"result-3\"><\/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>Thickness needed<\/span><\/span><span class=\"field-value\" id=\"result-4\" data-unit=\"in\"><\/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-5\"><span class=\"field-title\"><span>Thickness needed<\/span><\/span><span class=\"field-value\" id=\"result-5\" data-unit=\"mm\"><\/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-6\"><span class=\"field-title\"><span>Area to cover (incl. waste)<\/span><\/span><span class=\"field-value\" id=\"result-6\" data-unit=\"ft\u00b2\"><\/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-7\"><span class=\"field-title\"><span>Packages to buy<\/span><\/span><span class=\"field-value\" id=\"result-7\" data-unit=\"rolls \/ bags \/ kits\"><\/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-8\"><span class=\"field-title\"><span>Spray foam needed<\/span><\/span><span class=\"field-value\" id=\"result-8\" data-unit=\"board ft\"><\/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-9\"><span class=\"field-title\"><span>Estimated cost<\/span><\/span><span class=\"field-value\" id=\"result-9\"><\/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 is-column\" id=\"output-10\"><span class=\"field-title\"><span>Calculation notes<\/span><\/span><span class=\"field-value\" id=\"result-10\"><\/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=\"67405\" 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 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\\[ t = \\frac{R_{\\text{target}}}{R_{\\text{in}}} \\\\ A_{\\text{net}} = L \\times W - A_{\\text{open}} \\\\ A_{\\text{buy}} = A_{\\text{net}} \\times \\left(1 + \\frac{w}{100}\\right) \\\\ N = \\left\\lceil \\frac{A_{\\text{buy}}}{c} \\right\\rceil \\\\ \\text{BF} = A_{\\text{buy}} \\times t \\\\ C = N \\times p \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(t\\) \u2014 insulation thickness needed (in)<\/li>\n<li>\\(R_{\\text{target}}\\) \u2014 target R-value for the project (from DOE guidance or your custom value)<\/li>\n<li>\\(R_{\\text{in}}\\) \u2014 R-value per inch of the chosen material<\/li>\n<li>\\(L \\times W\\) \u2014 gross area (or a known total area)<\/li>\n<li>\\(A_{\\text{open}}\\) \u2014 window and door area to subtract<\/li>\n<li>\\(A_{\\text{net}}\\) \u2014 net area actually insulated (ft\u00b2)<\/li>\n<li>\\(w\\) \u2014 waste allowance for cuts, compression and settling (%)<\/li>\n<li>\\(A_{\\text{buy}}\\) \u2014 area to cover including waste (ft\u00b2)<\/li>\n<li>\\(c\\) \u2014 coverage of one package (ft\u00b2, or board ft for spray foam kits)<\/li>\n<li>\\(N\\) \u2014 packages, rolls or bags to buy (rounded up)<\/li>\n<li>\\(\\text{BF}\\) \u2014 board feet of spray foam (1 board ft = 1 ft\u00b2 covered 1 in thick)<\/li>\n<li>\\(C\\) \u2014 estimated material cost; \\(p\\) is price per package, per ft\u00b2, or per board ft<\/li>\n<\/ul>\n<p>The first equation converts a target R-value into a physical thickness, the rest turn that thickness and your area into a shopping list and a cost estimate. R-value adds up, so a wall or ceiling made of layers simply needs the layer R-values to sum to the target.<\/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 \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> insulating a 40 ft \u00d7 30 ft attic in DOE Climate Zone 4 (Kansas City) with fiberglass batts, 10% waste, rolls covering 80 ft\u00b2 each at $50 per roll.<\/p>\n<p>\\[ A_{\\text{net}} = 40 \\times 30 - 0 = 1200\\ \\text{ft}^2 \\]<br \/>\n\\[ R_{\\text{target}} = 60 \\quad (\\text{DOE guidance for attics in Zone 4}) \\]<br \/>\n\\[ t = \\frac{60}{3.1} \\approx 19.4\\ \\text{in} \\approx 492\\ \\text{mm} \\]<br \/>\n\\[ A_{\\text{buy}} = 1200 \\times 1.10 = 1320\\ \\text{ft}^2 \\]<br \/>\n\\[ N = \\left\\lceil \\frac{1320}{80} \\right\\rceil = 17\\ \\text{rolls} \\]<br \/>\n\\[ C = 17 \\times \\$50 = \\$850 \\]<\/p>\n<p><strong>Result:<\/strong> net area 1,200 ft\u00b2 (111.5 m\u00b2), target R-60, thickness needed \u2248 19.4 in (492 mm), area to cover 1,320 ft\u00b2, 17 rolls to buy, estimated cost $850.00 \u2014 material only.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to use the calculator<\/h2>\n<ol>\n<li><strong>Project<\/strong> \u2014 choose attic\/ceiling, exterior wall, or floor over unconditioned space. This determines which DOE recommendation applies.<\/li>\n<li><strong>DOE climate zone<\/strong> \u2014 pick the zone that matches your location (examples of cities are shown in each option).<\/li>\n<li><strong>Target R-value<\/strong> \u2014 select \"Use the DOE recommendation\" or \"Custom R-value\" and type your own number if you have a specific code requirement or energy goal.<\/li>\n<li><strong>Insulation type<\/strong> \u2014 pick the material; typical R-per-inch values are built in, or choose \"Custom material\" and type the R per inch printed on the product label or data sheet.<\/li>\n<li><strong>Stud \/ joist spacing<\/strong> \u2014 16 or 24 in on center; this is used in the notes to tell you which batt width to buy.<\/li>\n<li><strong>Area<\/strong> \u2014 measure with \"Rectangle (length \u00d7 width)\" or enter a known \"Total area\". Units can be ft, in, m, sq ft, sq yd or sq m.<\/li>\n<li><strong>Windows &amp; doors to subtract<\/strong> \u2014 total opening area you will not insulate; leave 0 for an open attic floor.<\/li>\n<li><strong>Coverage per package<\/strong> \u2014 ft\u00b2 covered by one roll, bag or package at the installed thickness; for spray foam kits, enter board feet instead.<\/li>\n<li><strong>Waste allowance<\/strong> \u2014 5\u201310% is typical to cover cuts, compression and settling.<\/li>\n<li><strong>Price<\/strong> \u2014 optional; enter $ per package, per ft\u00b2, or per board ft. Clear the field to skip the cost estimate.<\/li>\n<\/ol>\n<h2>What an R-value means<\/h2>\n<p>R-value measures how well a material resists heat flow: the higher the R-value, the better the insulation. It is defined per unit of area, so the total performance of an assembly is simply the sum of the R-values of its layers. R-values from different materials, thicknesses and products can be added directly \u2014 2 inches of R-3.1-per-inch fiberglass plus 1 inch of R-6.5 closed-cell foam gives roughly R-12.7.<\/p>\n<p>Because R-value is proportional to thickness, converting a target into inches is a single division: thickness = target R \u00f7 R per inch. A high-density material reaches the same R-value in less space, which matters a lot in walls, where the cavity depth is fixed by the stud size. A 2\u00d74 wall offers about 3.5 in of cavity depth and a 2\u00d76 wall about 5.5 in, so higher targets in a 2\u00d74 wall require high-density products or continuous exterior insulation.<\/p>\n<p>The recommendations built into this calculator come from U.S. DOE \/ ENERGY STAR guidance, which map each climate zone and assembly to a range \u2014 for example R49\u2013R60 for attics in colder zones. The calculator sizes to the upper end of the range, which is usually the better buy because attic insulation is cheap and the marginal cost of an extra inch is small. Codes in your jurisdiction may differ, so verify local requirements before purchasing.<\/p>\n<p>To compare results across metric and imperial sources, or to convert an R-value to a U-factor or RSI value, use the <a href=\"https:\/\/wpcalc.com\/en\/insulation-r-value-converter\/\">Insulation R-Value Converter<\/a>.<\/p>\n<h2>Practical tips, assumptions and limitations<\/h2>\n<ul>\n<li><strong>R per inch is typical, not exact.<\/strong> Fiberglass batts run R-2.9\u2013R-3.4 per inch depending on density; blown-in products vary with installed density. Always check the label and, for blown-in material, the coverage chart printed on the bag, which gives bag yield at each installed R-value and thickness.<\/li>\n<li><strong>Compression costs R-value.<\/strong> Squeezing an R-19 batt into a 3.5 in cavity does not give you R-19. Fit batts to the actual cavity depth, and never leave gaps or voids \u2014 a 4% gap can cut performance substantially.<\/li>\n<li><strong>Attics are sized loosely, walls are not.<\/strong> Ceiling insulation can simply be stacked or blown deeper, but wall thickness is limited by framing. The calculator's notes warn you when the required thickness exceeds a 2\u00d74 (3.5 in) or 2\u00d76 (5.5 in) cavity.<\/li>\n<li><strong>Blown-in coverage depends on the target.<\/strong> The same bag of cellulose covers fewer square feet at R-60 than at R-38. Enter the coverage figure for the thickness shown in your result, not a generic bag yield.<\/li>\n<li><strong>Spray foam is sold by board feet<\/strong> \u2014 one board ft is 1 ft\u00b2 covered 1 inch thick. Select \"board ft per kit\" and the calculator computes \\( A_{\\text{buy}} \\times t \\) automatically.<\/li>\n<li><strong>Batt width matters.<\/strong> For 16 in on-center framing buy 15 in wide batts (14.5 in between wood studs); for 24 in on-center, 23 in (22.5 in for wood studs).<\/li>\n<li><strong>The cost estimate is material only.<\/strong> It excludes labor, vapor retarders, attic baffles, fasteners and delivery. Prices also vary widely by region and product line.<\/li>\n<\/ul>\n<p>Once you know the area and thickness, our <a href=\"https:\/\/wpcalc.com\/en\/life\/square-footage-calculator\/\">Square Footage Calculator<\/a> helps double-check awkward room shapes, the <a href=\"https:\/\/wpcalc.com\/en\/life\/board-foot-calculator\/\">Board Foot Calculator<\/a> is handy for lumber you may need for furring or baffles, and the <a href=\"https:\/\/wpcalc.com\/en\/life\/drywall-calculator\/\">Drywall Calculator<\/a> finishes the interior side of the same wall.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Estimate how much insulation you need: enter your project, climate zone, area and material to get the target R-value, required thickness in inches or mm, number of rolls, bags or kits, and the material cost.<\/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":[6],"tags":[66],"class_list":["post-67405","post","type-post","status-publish","format-standard","hentry","category-life","tag-household"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/67405","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=67405"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/67405\/revisions"}],"predecessor-version":[{"id":67406,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/67405\/revisions\/67406"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=67405"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=67405"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=67405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}