{"id":56808,"date":"2015-11-30T18:06:12","date_gmt":"2015-11-30T16:06:12","guid":{"rendered":"http:\/\/wpcalc.com\/?p=56808"},"modified":"2026-09-30T18:03:50","modified_gmt":"2026-09-30T15:03:50","slug":"the-area-of-a-rectangular-duct","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/engineering\/the-area-of-a-rectangular-duct\/","title":{"rendered":"Area of Rectangular Duct Calculator"},"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\">Ventilation Duct Surface and Component Calculator<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"56808\" data-favorite-title=\"Area of Rectangular Duct\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/engineering\/the-area-of-a-rectangular-duct\/\" data-favorite-excerpt=\"Enter the side dimensions, length and quantity of a rectangular duct to get the total sheet-metal surface area, connector strip (shina) length and corner piece count, with an optional seam allowance.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-ventilation\">\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\/engineering\/the-area-of-a-rectangular-duct\/\" method=\"POST\" class=\"calculator\" id=\"calculator-56808\" data-post=\"56808\"><fieldset class=\"fieldset-input\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Side A<\/label><div class=\"term\">A<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"side_a\" id=\"field-1\" aria-describedby=\"calc-unit-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"Side A\" min=\"0\" value=\"500\"\/><div class=\"unit\" id=\"calc-unit-1\">mm<\/div><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-2\">Side B<\/label><div class=\"term\">B<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"side_b\" id=\"field-2\" aria-describedby=\"calc-unit-2\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"Side B\" min=\"0\" value=\"300\"\/><div class=\"unit\" id=\"calc-unit-2\">mm<\/div><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-3\">Length<\/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=\"length\" id=\"field-3\" aria-describedby=\"calc-unit-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"Length\" min=\"0\" value=\"1000\"\/><div class=\"unit\" id=\"calc-unit-3\">mm<\/div><\/div><div class=\"field has-term\" id=\"input-4\"><label for=\"field-4\">Number<\/label><div class=\"term\">N<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"number\" id=\"field-4\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"Number of ducts\" min=\"1\" value=\"1\"\/><\/div><div class=\"field is-checkbox\" id=\"input-5\"><input type=\"checkbox\" id=\"field-5\" value=\"1\"\/><label for=\"field-5\">Consider seams<\/label><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"56808\">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>Area products<\/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 class=\"field-result\" id=\"output-2\"><span class=\"field-title\"><span>Tire<\/span><\/span><span class=\"field-value\" id=\"result-2\"><\/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>Corner<\/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><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=\"56808\" 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\">39<\/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\">11<\/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\">7<\/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\">2<\/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\">37<\/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>Area of Rectangular Duct 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\\[ A_s = 2\\left(\\frac{A}{1000} + \\frac{B}{1000} + SC\\right) \\cdot \\frac{L}{1000} \\cdot N \\\\ P_s = 2\\left(\\left(\\frac{A}{1000} + \\frac{B}{1000}\\right) \\cdot 2 - S\\right) \\cdot N \\\\ N_c = 8 \\cdot N \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(A\\), \\(B\\) \u2014 side dimensions of the duct cross-section (mm)<\/li>\n<li>\\(L\\) \u2014 length of one duct section (mm)<\/li>\n<li>\\(N\\) \u2014 number of duct sections<\/li>\n<li>\\(A_s\\) \u2014 total surface area of the duct walls (m\u00b2)<\/li>\n<li>\\(P_s\\) \u2014 total length of the connector strip, or shina, for the flanges (m)<\/li>\n<li>\\(N_c\\) \u2014 number of flange corner pieces (pcs)<\/li>\n<li>\\(SC = 0.02\\) m if seams are considered, otherwise \\(SC = 0\\)<\/li>\n<li>\\(S = 0.12\\) m if seams are considered, otherwise \\(S = 0\\)<\/li>\n<\/ul>\n<p>All dimensions are entered in millimetres and converted to metres inside the formula. The first expression is the perimeter of the duct cross-section (plus the seam allowance) multiplied by the length; the second gives the total strip length needed for the flange frames on both duct ends; the third counts eight corner pieces per duct section \u2014 four for each end flange.<\/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>Area of Rectangular Duct \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> a straight rectangular duct with Side A = 500 mm, Side B = 300 mm, Length = 1000 mm, one duct section, and seams considered.<\/p>\n<p>\\[ A_s = 2\\left(0.5 + 0.3 + 0.02\\right) \\cdot 1 \\cdot 1 = 1.64 \\ \\text{m}^2 \\]<\/p>\n<p>\\[ P_s = 2\\left(\\left(0.5 + 0.3\\right) \\cdot 2 - 0.12\\right) \\cdot 1 = 2.96 \\ \\text{m} \\]<\/p>\n<p>\\[ N_c = 8 \\cdot 1 = 8 \\ \\text{pcs} \\]<\/p>\n<p><strong>Result:<\/strong> surface area of the duct walls \u2014 1.64 m\u00b2; connector strip (shina) \u2014 2.96 m (shown as 2.96 m\u00b2 in the result field); corner pieces \u2014 8 pcs.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>Enter <strong>Side A<\/strong> \u2014 the first dimension of the duct cross-section, in millimetres (e.g. 500).<\/li>\n<li>Enter <strong>Side B<\/strong> \u2014 the second dimension of the duct cross-section, in millimetres (e.g. 300).<\/li>\n<li>Enter <strong>Length<\/strong> \u2014 the length of one straight duct section, in millimetres (e.g. 1000).<\/li>\n<li>Enter <strong>Number<\/strong> \u2014 how many identical duct sections you need to fabricate.<\/li>\n<li>Leave <strong>Consider seams<\/strong> checked if the ducts will be made with folded seams (Pittsburgh lock or similar). This adds a 20 mm allowance per side to the surface area and subtracts 120 mm from the shina length to account for the corner cuts. Uncheck it for a pure geometric calculation.<\/li>\n<li>Read the results: <strong>Area products<\/strong> \u2014 total sheet-metal surface area; <strong>Tire<\/strong> \u2014 total shina (flange strip) length; <strong>Corner<\/strong> \u2014 number of flange corner pieces.<\/li>\n<\/ol>\n<h2>What the Results Mean<\/h2>\n<p>The <strong>Area products<\/strong> value is the total area of the four duct walls. This is the number you need when ordering galvanized sheet metal, and it is also the basis for estimating insulation, sealant and paint. Note that it is the surface area of the finished duct, not the flat blank size \u2014 fabricators still add their own folding and joint allowances when cutting the sheet.<\/p>\n<p>The <strong>Tire<\/strong> result (from \"shina\", the term for the flange strip used in duct fabrication) is the total length of the connector profile that frames both ends of the duct. This flange strip is mounted along the perimeter of each duct end so that sections can be bolted together with gaskets. The formula takes the cross-section perimeter, subtracts the space taken up by the corner pieces, and multiplies by two for the two ends of the duct.<\/p>\n<p>The <strong>Corner<\/strong> result is simply eight corner pieces per duct section \u2014 four corners on each of the two end flanges. These stamped or extruded corners hold the flange strip together and provide the bolt holes for connecting duct sections.<\/p>\n<p>Together, these three figures cover the main bill of materials for a straight rectangular duct: sheet metal for the walls, strip for the flanges, and corners for the frame. For a complete ventilation project you will also need fittings (bends, tees, reducers), which this straight-duct calculation does not include. To size the ductwork itself, first determine the required airflow with the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/ventilation\/\">Ventilation Airflow Requirement<\/a> calculator, then check fan capacity with the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/ventilation-2\/\">Ventilation Power<\/a> calculator.<\/p>\n<h2>Assumptions and Practical Tips<\/h2>\n<ul>\n<li>The calculator handles <strong>straight duct sections only<\/strong>. Bends, tees, reducers and other fittings must be estimated separately.<\/li>\n<li>The seam allowance is fixed: 0.02 m (20 mm) added to the half-perimeter for the surface area, and 0.12 m (120 mm) deducted from the shina length. If your fabrication technology uses different allowances, uncheck <strong>Consider seams<\/strong> and adjust the results manually.<\/li>\n<li>The <strong>Tire<\/strong> result is a linear quantity (metres of strip), even though the calculator displays it with an m\u00b2 suffix \u2014 treat the number as a length when ordering the flange strip.<\/li>\n<li>Sheet thickness and material grade are not accounted for; add a waste margin of 5\u201310% to the surface area when ordering metal.<\/li>\n<li>All inputs must be in millimetres. The results are converted to metres automatically.<\/li>\n<\/ul>\n<p>Once the ducts are sized and fabricated, you can complete the system layout with the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/number-of-diffusers\/\">Ventilation Diffuser Count<\/a> and <a href=\"https:\/\/wpcalc.com\/en\/engineering\/number-of-grids\/\">Ventilation Grid Count<\/a> calculators to distribute the air correctly in each room.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Enter the side dimensions, length and quantity of a rectangular duct to get the total sheet-metal surface area, connector strip (shina) length and corner piece count, with an optional seam allowance.<\/p>\n","protected":false},"author":70,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[4],"tags":[39],"class_list":["post-56808","post","type-post","status-publish","format-standard","hentry","category-engineering","tag-ventilation"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/56808","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=56808"}],"version-history":[{"count":3,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/56808\/revisions"}],"predecessor-version":[{"id":65943,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/56808\/revisions\/65943"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=56808"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=56808"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=56808"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}