{"id":66722,"date":"2026-10-13T08:44:13","date_gmt":"2026-10-13T05:44:13","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66722"},"modified":"2026-10-13T08:44:13","modified_gmt":"2026-10-13T05:44:13","slug":"rebar-spacing-and-count","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/engineering\/rebar-spacing-and-count\/","title":{"rendered":"Rebar Spacing and Count"},"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\">Fit Rebar Evenly Across a Slab or Footing<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66722\" data-favorite-title=\"Rebar Count\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/engineering\/rebar-spacing-and-count\/\" data-favorite-excerpt=\"Work out how many rebar bars fit evenly across a slab, footing or wall and the exact equal centre-to-centre spacing. Enter the placement width, edge cover and target spacing.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-engineering\">\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\/rebar-spacing-and-count\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66722\" data-post=\"66722\"><fieldset class=\"fieldset-input is-2\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Placement width (W)<\/label><div class=\"term\">W<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"text\" name=\"placement_width_w\" id=\"field-1\" aria-describedby=\"calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"300\" min=\"0.01\" value=\"300\"\/><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"unit\" aria-label=\"Unit\"><option value=\"cm\" selected>cm<\/option><option value=\"m\">m<\/option><option value=\"mm\">mm<\/option><option value=\"in\">in<\/option><option value=\"ft\">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-1\">Overall slab, footing or wall dimension across which the bars are distributed<\/small><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-3\">Edge cover (c)<\/label><div class=\"term\">c<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"text\" name=\"edge_cover_c\" id=\"field-3\" aria-describedby=\"calc-info-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"5\" min=\"0\" value=\"5\"\/><div class=\"grid grid-cols-1\"><select id=\"field-4\" name=\"unit\" aria-label=\"Unit\"><option value=\"cm\" selected>cm<\/option><option value=\"m\">m<\/option><option value=\"mm\">mm<\/option><option value=\"in\">in<\/option><option value=\"ft\">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-3\">Concrete cover kept clear at each edge (applied on both sides)<\/small><\/div><div class=\"field is-single has-term\" id=\"input-3\"><label for=\"field-5\">Target spacing (s)<\/label><div class=\"term\">s<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"text\" name=\"target_spacing_s\" id=\"field-5\" aria-describedby=\"calc-info-5\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"20\" min=\"0.01\" value=\"20\"\/><div class=\"grid grid-cols-1\"><select id=\"field-6\" name=\"unit\" aria-label=\"Unit\"><option value=\"cm\" selected>cm<\/option><option value=\"m\">m<\/option><option value=\"mm\">mm<\/option><option value=\"in\">in<\/option><option value=\"ft\">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-5\">Maximum desired centre-to-centre distance between bars; the actual spacing is adjusted so it never exceeds this<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66722\">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> Rebar Layout<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Required number of bars<\/span><span class=\"result-term\">n<\/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>Resulting equal spacing (c\/c)<\/span><span class=\"result-term\">s\u2090<\/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 is-column\" id=\"output-3\"><span class=\"field-title\"><span>Formula and notes<\/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=\"66722\" 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>Rebar Count 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\\[ n = \\left\\lfloor \\frac{W - 2c}{s} \\right\\rfloor + 1 \\\\\n\\[ s_a = \\frac{W - 2c}{n - 1} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(W\\) \u2014 placement width, the overall slab, footing or wall dimension across which the bars are distributed<\/li>\n<li>\\(c\\) \u2014 edge cover, the concrete kept clear at each edge (applied on both sides)<\/li>\n<li>\\(s\\) \u2014 target maximum centre-to-centre spacing between bars<\/li>\n<li>\\(n\\) \u2014 required number of bars<\/li>\n<li>\\(s_a\\) \u2014 resulting equal centre-to-centre spacing<\/li>\n<\/ul>\n<p>One bar is placed at each edge of the clear span \\(W - 2c\\), and the remaining bars are spread evenly in between, so the actual spacing \\(s_a\\) is the same for every gap.<\/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>Rebar Count \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> a slab section 300 cm wide, with 5 cm of concrete cover at each edge and a target spacing of 20 cm.<\/p>\n<p>\\[ W - 2c = 300 - 2 \\times 5 = 290 \\text{ cm} \\]<\/p>\n<p>\\[ n = \\left\\lfloor \\frac{290}{20} \\right\\rfloor + 1 = 14 + 1 = 15 \\text{ bars} \\]<\/p>\n<p>\\[ s_a = \\frac{290}{15 - 1} = \\frac{290}{14} \\approx 20.71 \\text{ cm} \\]<\/p>\n<p><strong>Result:<\/strong> 15 bars, at an equal centre-to-centre spacing of approximately 20.71 cm (\u2248 8.15 in). Note that the equalized spacing is slightly wider than the 20 cm target \u2014 see the practical tips below.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to use the calculator<\/h2>\n<ol>\n<li>Enter the <strong>Placement width (W)<\/strong> \u2014 the full dimension of the slab, footing or wall across which the bars will be distributed.<\/li>\n<li>Enter the <strong>Edge cover (c)<\/strong> \u2014 the clear concrete distance kept at each side. It is applied on both edges, so the clear span between the two outermost bars is \\(W - 2c\\).<\/li>\n<li>Enter the <strong>Target spacing (s)<\/strong> \u2014 the maximum centre-to-centre distance you want between bars.<\/li>\n<li>Select the unit (cm, m, mm, in or ft) next to each value; the three inputs do not have to share the same unit.<\/li>\n<li>Read the results: the <strong>required number of bars<\/strong>, the <strong>resulting equal spacing (c\/c)<\/strong>, and the formula with notes on typical cover and spacing limits.<\/li>\n<\/ol>\n<h2>What rebar spacing and count mean<\/h2>\n<p>Reinforcing bars in a slab, footing or wall are rarely placed at random: they are laid out on a regular grid, measured centre to centre, with a clear concrete cover at the edges to protect the steel from corrosion and fire. The number of bars and their spacing directly control how much steel crosses a given section, and therefore how well the concrete resists bending, cracking and shrinkage.<\/p>\n<p>This calculator answers a very practical question: given a width, a cover and a maximum allowed spacing, how many bars do I actually need, and where do they go? Because the clear span \\(W - 2c\\) almost never divides evenly by the target spacing, the bars cannot sit at exactly the target distance and still land symmetrically. The standard solution is to place one bar at each edge of the clear span and distribute the rest evenly, which is what the formula does \u2014 the result is a layout that is simple to mark out and build on site.<\/p>\n<p>When you interpret the output, remember that the spacing is centre-to-centre, not the clear gap between bar surfaces. If you are using, say, 16 mm bars at 20 cm centres, the clear gap between bars is only about 18.4 cm. Also note that the equalized spacing \\(s_a\\) can end up marginally <em>wider<\/em> than the target when the division is not exact \u2014 the section below explains what to do if your specification is strict.<\/p>\n<h2>Assumptions, limitations and practical tips<\/h2>\n<ul>\n<li><strong>Cover is applied on both sides.<\/strong> Make sure you enter the cover for one edge only; the calculator subtracts it twice. Typical concrete cover is 40\u201350 mm (1.5\u20132 in) for slabs on ground and footings, but your design code governs \u2014 check the minimum cover for your exposure conditions.<\/li>\n<li><strong>Spacing limits.<\/strong> Most codes cap the maximum bar spacing, often at about three times the slab thickness or roughly 450\u2013460 mm, whichever is smaller. Your target spacing should already respect these limits.<\/li>\n<li><strong>Strict compliance.<\/strong> Because the calculator floors the intermediate count, the equalized spacing can slightly exceed the target (as in the example above, 20.71 cm vs 20 cm). If your specification requires the spacing to stay at or below the maximum, add one more bar: 16 bars in the example would give \\(290 \/ 15 \\approx 19.33\\) cm, comfortably under the limit.<\/li>\n<li><strong>Minimum steel.<\/strong> This tool only counts bars for a chosen spacing; it does not check whether that amount of reinforcement satisfies minimum steel ratio, crack control or bending capacity requirements. A structural check is still needed for final design \u2014 see the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/beam-section-modulus\/\">section modulus calculator<\/a> and the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/simply-supported-beam-with-uniform-load\/\">uniformly loaded simply supported beam calculator<\/a> for related strength checks.<\/li>\n<li><strong>Two-way slabs.<\/strong> Run the calculation separately for each direction; corner and edge details may require additional bars that this simple one-dimensional layout does not include.<\/li>\n<\/ul>\n<p>For layout work on site, the resulting equal spacing is usually rounded to a convenient marking dimension (e.g. 20.7 cm marked every 20.7 cm, or slightly adjusted to hit whole numbers on your tape). For other construction planning tasks, such as <a href=\"https:\/\/wpcalc.com\/en\/engineering\/stair-rise-and-run\/\">stair rise and run<\/a>, the same even-distribution logic applies.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Work out how many rebar bars fit evenly across a slab, footing or wall and the exact equal centre-to-centre spacing. Enter the placement width, edge cover and target spacing.<\/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":[4],"tags":[96],"class_list":["post-66722","post","type-post","status-publish","format-standard","hentry","category-engineering","tag-concrete"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66722","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=66722"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66722\/revisions"}],"predecessor-version":[{"id":66723,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66722\/revisions\/66723"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66722"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66722"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66722"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}