{"id":56800,"date":"2015-11-30T18:02:23","date_gmt":"2015-11-30T16:02:23","guid":{"rendered":"http:\/\/wpcalc.com\/?p=56800"},"modified":"2026-09-30T18:42:08","modified_gmt":"2026-09-30T15:42:08","slug":"number-of-grids","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/engineering\/number-of-grids\/","title":{"rendered":"Ventilation Grid Count 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\">Calculate Required Number of Ventilation Grids<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"56800\" data-favorite-title=\"Ventilation Grid Count\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/engineering\/number-of-grids\/\" data-favorite-excerpt=\"Calculate the number of ventilation grids needed from the air flow rate (m\u00b3\/h), air speed (m\/s), and the open area of one grid (m\u00b2). Enter your values and get the required grid count instantly.\" 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\/number-of-grids\/\" method=\"POST\" class=\"calculator\" id=\"calculator-56800\" data-post=\"56800\"><fieldset class=\"fieldset-input is-3\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Air flow<\/label><div class=\"term\">Q<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"air_flow\" id=\"field-1\" aria-describedby=\"calc-unit-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"Enter air flow\" min=\"0\" value=\"500\"\/><div class=\"unit\" id=\"calc-unit-1\">m\u00b3\/h<\/div><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-2\">Air speed<\/label><div class=\"term\">v<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"air_speed\" id=\"field-2\" aria-describedby=\"calc-unit-2\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"Enter air speed\" min=\"0\" value=\"3\"\/><div class=\"unit\" id=\"calc-unit-2\">m\/s<\/div><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-3\">Open area of lattice<\/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=\"open_area_of_lattice\" id=\"field-3\" aria-describedby=\"calc-unit-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"Enter open area\" min=\"0\" value=\"0.1\"\/><div class=\"unit\" id=\"calc-unit-3\">m\u00b2<\/div><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"56800\">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>Required number of grids<\/span><\/span><span class=\"field-value\" id=\"result-1\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><\/div><div class=\"result-actions\"><button type=\"button\" class=\"copy-link\"><svg viewBox=\"0 0 20 20\" fill=\"currentColor\" aria-hidden=\"true\"><path d=\"M12.232 4.232a2.5 2.5 0 0 1 3.536 3.536l-1.225 1.224a.75.75 0 0 0 1.061 1.06l1.224-1.224a4 4 0 0 0-5.656-5.656l-3 3a4 4 0 0 0 .225 5.865.75.75 0 0 0 .977-1.138 2.5 2.5 0 0 1-.142-3.667l3-3Z\"\/><path d=\"M11.603 7.963a.75.75 0 0 0-.977 1.138 2.5 2.5 0 0 1 .142 3.667l-3 3a2.5 2.5 0 0 1-3.536-3.536l1.225-1.224a.75.75 0 0 0-1.061-1.06l-1.224 1.224a4 4 0 1 0 5.656 5.656l3-3a4 4 0 0 0-.225-5.865Z\"\/><\/svg><span class=\"copy-link__text\">Copy link to this calculation<\/span><\/button><span class=\"sr-only\" role=\"status\" id=\"copy-link-status\"><\/span><\/div><\/div><a href=\"#respond\" class=\"hidden transition-opacity duration-300 opacity-0 w-50 text-sm justify-center items-center gap-2 px-4 py-2 rounded bg-gray-200 text-gray-700 hover:bg-gray-300\" id=\"leave-comment\"><span class=\"icon icon-comments\" aria-hidden=\"true\"><\/span>Leave a Comment<\/a><\/form><\/section><section id=\"calc-reactions\" class=\"not-prose hidden my-12 bg-gradient-to-r from-primary-50 to-gray-50 border border-indigo-100 rounded-xl px-6 py-4 shadow-sm\" data-post=\"56800\" 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>Ventilation Grid 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\\lceil \\frac{Q}{3600 \\cdot v \\cdot A} \\right\\rceil \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(Q\\) \u2014 air flow rate (m\u00b3\/h)<\/li>\n<li>\\(v\\) \u2014 air velocity through the grids (m\/s)<\/li>\n<li>\\(A\\) \u2014 open (free) area of a single grid (m\u00b2)<\/li>\n<li>\\(N\\) \u2014 required number of grids, rounded up to the next whole number with the ceiling function \\(\\lceil \\cdot \\rceil\\)<\/li>\n<\/ul>\n<p>The factor 3600 converts the air flow from cubic meters per hour to cubic meters per second, so that all units match. The formula finds how many grids of open area \\(A\\) are needed to pass the air flow \\(Q\\) without the velocity through each grid exceeding \\(v\\).<\/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>Ventilation Grid Count \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> a ventilation system must supply 500 m\u00b3\/h of air. The recommended air speed through the grids is 3 m\/s, and each grid has an open area of 0.1 m\u00b2.<\/p>\n<p>\\[ N = \\left\\lceil \\frac{500}{3600 \\cdot 3 \\cdot 0.1} \\right\\rceil = \\left\\lceil \\frac{500}{1080} \\right\\rceil = \\left\\lceil 0.46 \\right\\rceil = 1 \\]<\/p>\n<p><strong>Result:<\/strong> 1 grid is required. A single grid with 0.1 m\u00b2 of open area is enough, since at 500 m\u00b3\/h the actual velocity through it stays well below the 3 m\/s limit.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>Enter the <strong>Air flow<\/strong> \\(Q\\) that the system must handle, in m\u00b3\/h.<\/li>\n<li>Enter the <strong>Air speed<\/strong> \\(v\\) you want to allow through the grids, in m\/s. Typical values are 2\u20133 m\/s for supply grilles in occupied rooms; higher speeds increase noise.<\/li>\n<li>Enter the <strong>Open area of lattice<\/strong> \\(A\\) \u2014 the effective free area of one grid in m\u00b2, not the overall face dimensions. Manufacturers list this value in their product data.<\/li>\n<li>Read the <strong>Required number of grids<\/strong>, which is always rounded up to the next whole grid.<\/li>\n<\/ol>\n<h2>What the Calculation Means<\/h2>\n<p>A ventilation grid (grille or lattice) can only pass a limited amount of air. The air flow through one grid equals its open area multiplied by the air velocity across that area: \\(q = v \\cdot A\\) in m\u00b3\/s. If you try to push too much air through too little open area, the velocity rises, which causes pressure drop, noise, and uncomfortable drafts in the occupied zone.<\/p>\n<p>To find the total free area needed, the hourly flow is first converted to m\u00b3\/s by dividing by 3600, then divided by the chosen velocity:<\/p>\n<p>\\[ A_{total} = \\frac{Q}{3600 \\cdot v} \\]<\/p>\n<p>Dividing this by the open area of a single grid gives the grid count, and the result is rounded up because you cannot install a fraction of a grid. Note that the open area is usually much smaller than the nominal face area of the grille \u2014 a 300 \u00d7 150 mm grille has a face of 0.045 m\u00b2, but its open area may be only 50\u201370% of that depending on the blade geometry.<\/p>\n<p>The result should be interpreted as a minimum count. In practice you may distribute more, smaller grilles around the room for better air distribution, or select a larger grid to reduce the count. If you also need to size the ductwork feeding the grids, see the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/the-area-of-a-rectangular-duct\/\">Area of Rectangular Duct calculator<\/a>.<\/p>\n<h2>Assumptions, Limitations and Tips<\/h2>\n<ul>\n<li>The calculation assumes the air flow is evenly distributed between all grids and that each grid sees the same velocity. Uneven duct or plenum design can make some grids pass much more air than others.<\/li>\n<li>The open area \\(A\\) must be the <em>effective<\/em> free area from the manufacturer's data sheet. Using the face (outer) area of the grille overestimates the capacity and gives too few grids.<\/li>\n<li>The ceiling rounding means the actual velocity will be slightly lower than the design value \u2014 that is fine. Never round down: the grids would then run faster than intended and become noisy.<\/li>\n<li>Very high face velocities (above roughly 4\u20135 m\/s for room grilles) generate audible noise. If your grid count comes out surprisingly low, check that the velocity assumption matches the application: residential grilles 1.5\u20133 m\/s, commercial grilles up to 4\u20135 m\/s, industrial louvers higher.<\/li>\n<li>This tool sizes the grids only. To determine how much air the room needs in the first place, use the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/ventilation\/\">Ventilation Airflow Requirement calculator<\/a> or the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/ventilation-in-the-number-of-people\/\">Ventilation per Number of People calculator<\/a>.<\/li>\n<li>If your system uses ceiling diffusers instead of wall grids, the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/number-of-diffusers\/\">Ventilation Diffuser Count calculator<\/a> handles that case, and the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/ventilation-2\/\">Ventilation Power calculator<\/a> helps estimate the fan power needed to move the air.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Calculate the number of ventilation grids needed from the air flow rate (m\u00b3\/h), air speed (m\/s), and the open area of one grid (m\u00b2). Enter your values and get the required grid count instantly.<\/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-56800","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\/56800","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=56800"}],"version-history":[{"count":3,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/56800\/revisions"}],"predecessor-version":[{"id":66028,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/56800\/revisions\/66028"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=56800"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=56800"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=56800"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}