{"id":66917,"date":"2026-10-13T10:14:26","date_gmt":"2026-10-13T07:14:26","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66917"},"modified":"2026-10-13T10:14:26","modified_gmt":"2026-10-13T07:14:26","slug":"bet-surface-area-calculator","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/chemistry\/bet-surface-area-calculator\/","title":{"rendered":"BET Surface Area 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\">Find the Specific Surface Area from the BET Monolayer Capacity<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66917\" data-favorite-title=\"BET Surface Area\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/chemistry\/bet-surface-area-calculator\/\" data-favorite-excerpt=\"Calculate the BET specific surface area (m\u00b2\/g) of a powder or porous material from the monolayer capacity, molecular cross-sectional area, and sample mass. Works with mol, mmol, or cm\u00b3 (STP) input.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-molecule\">\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\/chemistry\/bet-surface-area-calculator\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66917\" data-post=\"66917\"><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\">Monolayer Amount (nm)<\/label><div class=\"term\">nm<\/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=\"monolayer_amount_nm\" id=\"field-1\" aria-describedby=\"calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 22.5\" min=\"0\" value=\"22.5\"\/><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"unit\" aria-label=\"Unit\"><option value=\"mol\">mol<\/option><option value=\"mmol\">mmol<\/option><option value=\"umol\">\u00b5mol<\/option><option value=\"cm3_stp\" selected>cm\u00b3 (STP)<\/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\">Monolayer capacity nm from the BET plot (1\/c intercept). Gas volumes refer to STP (0 \u00b0C, 1 atm), where 1 mol = 22,414 cm\u00b3.<\/small><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-3\">Molecular Cross-Sectional Area (Am)<\/label><div class=\"term\">Am<\/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=\"molecular_crosssectional_area_am\" id=\"field-3\" aria-describedby=\"calc-info-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.162\" min=\"0\" value=\"0.162\"\/><div class=\"grid grid-cols-1\"><select id=\"field-4\" name=\"unit\" aria-label=\"Unit\"><option value=\"nm2\" selected>nm\u00b2<\/option><option value=\"A2\">\u00c5\u00b2<\/option><option value=\"pm2\">pm\u00b2<\/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\">Occupied area per adsorbate molecule: N\u2082 at 77 K \u2248 0.162 nm\u00b2 (16.2 \u00c5\u00b2), Ar \u2248 0.142 nm\u00b2, Kr \u2248 0.195 nm\u00b2, CO\u2082 \u2248 0.170 nm\u00b2.<\/small><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-5\">Sample Mass (m)<\/label><div class=\"term\">m<\/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=\"sample_mass_m\" id=\"field-5\" aria-describedby=\"calc-info-5\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 1\" min=\"0\" value=\"1\"\/><div class=\"grid grid-cols-1\"><select id=\"field-6\" name=\"unit\" aria-label=\"Unit\"><option value=\"g\" selected>g<\/option><option value=\"mg\">mg<\/option><option value=\"kg\">kg<\/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\">Mass of the degassed sample actually placed in the BET cell.<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66917\">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> BET Surface Area Results<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Specific Surface Area (SBET)<\/span><span class=\"result-term\">SBET<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"m\u00b2\/g\"><\/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-2\"><span class=\"field-title\"><span>Total Area and Other Units<\/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>Calculation Details<\/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 is-column\" id=\"output-4\"><span class=\"field-title\"><span>About BET Surface Area<\/span><\/span><span class=\"field-value\" id=\"result-4\"><\/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=\"66917\" 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>BET Surface Area<\/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\\[ S_{BET} = \\frac{n_m \\cdot N_A \\cdot A_m}{m} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(n_m\\) \u2014 monolayer capacity, the amount of adsorbate gas covering the entire surface exactly one molecule thick (mol)<\/li>\n<li>\\(N_A\\) \u2014 Avogadro constant, \\(6.02214076 \\times 10^{23}\\) mol\u207b\u00b9 (exact SI value)<\/li>\n<li>\\(A_m\\) \u2014 molecular cross-sectional area of the adsorbate (m\u00b2 per molecule)<\/li>\n<li>\\(m\\) \u2014 mass of the degassed sample (g)<\/li>\n<li>\\(S_{BET}\\) \u2014 specific surface area (m\u00b2\/g)<\/li>\n<\/ul>\n<p>The formula counts the molecules in a close-packed monolayer (\\(n_m \\cdot N_A\\)), multiplies by the area each molecule occupies, and normalizes by the sample mass to give the surface area per gram.<\/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>BET Surface Area \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> a nitrogen adsorption isotherm at 77 K on a 1 g silica sample gives a monolayer volume of 22.5 cm\u00b3 (STP). Using the standard cross-sectional area of N\u2082, \\(A_m\\) = 0.162 nm\u00b2, calculate the BET surface area.<\/p>\n<p>Convert the monolayer volume to moles using the molar volume of an ideal gas at STP (22,414 cm\u00b3\/mol, the same relationship used in <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/avogadros-law-calculator\/\">Avogadro's law<\/a>):<\/p>\n<p>\\[ n_m = \\frac{22.5 \\text{ cm}^3}{22{,}414 \\text{ cm}^3\/\\text{mol}} = 1.004 \\times 10^{-3} \\text{ mol} \\]<\/p>\n<p>Count the molecules in the monolayer and multiply by the area of each one:<\/p>\n<p>\\[ N = 1.004 \\times 10^{-3} \\times 6.022 \\times 10^{23} = 6.045 \\times 10^{20} \\text{ molecules} \\]<\/p>\n<p>\\[ S = 6.045 \\times 10^{20} \\times 0.162 \\times 10^{-18} \\text{ m}^2 = 97.9 \\text{ m}^2 \\]<\/p>\n<p><strong>Result:<\/strong> \\( S_{BET} = 97.9 \/ 1 \\text{ g} \\approx 97.9 \\) m\u00b2\/g \u2014 a typical value for a mesoporous silica or fine oxide powder.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the BET Surface Area Calculator<\/h2>\n<ol>\n<li>Enter the <strong>Monolayer Amount (nm)<\/strong> obtained from your BET plot (the reciprocal of the intercept, \\(1\/c\\)) and choose its unit: <code>mol<\/code>, <code>mmol<\/code>, <code>\u00b5mol<\/code>, or <code>cm\u00b3 (STP)<\/code>. Gas volumes must refer to STP (0 \u00b0C, 1 atm).<\/li>\n<li>Enter the <strong>Molecular Cross-Sectional Area (Am)<\/strong> of the adsorbate and select <code>nm\u00b2<\/code>, <code>\u00c5\u00b2<\/code>, or <code>pm\u00b2<\/code>. The default 0.162 nm\u00b2 is the standard value for N\u2082 at 77 K.<\/li>\n<li>Enter the <strong>Sample Mass (m)<\/strong> of the degassed sample in the BET cell, in <code>g<\/code>, <code>mg<\/code>, or <code>kg<\/code>.<\/li>\n<li>Read the <strong>Specific Surface Area (SBET)<\/strong> in m\u00b2\/g, together with the total sample area, alternative units, and a step-by-step calculation breakdown.<\/li>\n<\/ol>\n<h2>What Is BET Surface Area?<\/h2>\n<p>The BET method (Brunauer\u2013Emmett\u2013Teller) is the standard technique for measuring the surface area of porous or finely divided solids \u2014 catalysts, activated carbons, zeolites, MOFs, pigments, and pharmaceutical powders. The sample is cooled, usually to 77 K, and gas is adsorbed onto its surface at increasing relative pressures. The BET transform of the isotherm, \\( p\/[v(p_0 - p)] \\) plotted against \\( p\/p_0 \\), is linear in the range \\( p\/p_0 \\approx 0.05\\text{\u2013}0.30 \\); the intercept and slope of that line give the monolayer capacity \\(n_m\\), the amount of gas needed to cover the whole surface exactly one molecule thick.<\/p>\n<p>Once \\(n_m\\) is known, the surface area follows directly: multiplying by the Avogadro constant counts the molecules in the monolayer, and multiplying by the molecular cross-sectional area \\(A_m\\) gives the total area those molecules cover. Dividing by the sample mass yields the specific surface area \\(S_{BET}\\) in m\u00b2\/g, the number nearly always reported in materials characterization.<\/p>\n<p>Interpreting the result: values below ~10 m\u00b2\/g are considered low (typical of coarse non-porous powders), 100\u2013500 m\u00b2\/g is common for porous silicas and aluminas, and above ~1000 m\u00b2\/g is the realm of highly porous materials such as activated carbons, zeolites, and metal-organic frameworks. Because surface area drives adsorption, catalysis, and dissolution behavior, \\(S_{BET}\\) is a key quality-control and research parameter.<\/p>\n<h2>Choosing the Molecular Cross-Sectional Area<\/h2>\n<p>The accuracy of the result depends strongly on using the correct \\(A_m\\) for your adsorbate and temperature:<\/p>\n<table>\n<thead>\n<tr>\n<th>Adsorbate<\/th>\n<th>Temperature<\/th>\n<th>Am (nm\u00b2)<\/th>\n<th>Am (\u00c5\u00b2)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>N\u2082 (standard)<\/td>\n<td>77 K<\/td>\n<td>0.162<\/td>\n<td>16.2<\/td>\n<\/tr>\n<tr>\n<td>Ar<\/td>\n<td>87 K<\/td>\n<td>0.142<\/td>\n<td>14.2<\/td>\n<\/tr>\n<tr>\n<td>Kr<\/td>\n<td>77 K<\/td>\n<td>0.195\u20130.210<\/td>\n<td>19.5\u201321.0<\/td>\n<\/tr>\n<tr>\n<td>CO\u2082<\/td>\n<td>273 K<\/td>\n<td>0.170<\/td>\n<td>17.0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Nitrogen at 77 K is the default choice for most routine analyses. For low-surface-area samples (below ~10 m\u00b2\/g), krypton is preferred because its very low saturation pressure reduces the uncertainty of the dead-volume correction. CO\u2082 at 273 K is used for micropore analysis because it accesses ultramicropores that N\u2082 enters slowly at 77 K.<\/p>\n<h2>Assumptions, Limitations, and Practical Tips<\/h2>\n<ul>\n<li><strong>Close-packed monolayer:<\/strong> the calculation assumes each molecule occupies its tabulated cross-sectional area in a hexagonal close-packed layer. Real packing can deviate, introducing uncertainties of roughly 5\u201320%.<\/li>\n<li><strong>Validity range:<\/strong> the BET model is only reliable in the linear region of the BET plot (\\(p\/p_0 \\approx 0.05\\text{\u2013}0.30\\)). Outside this range the monolayer capacity \u2014 and therefore \\(S_{BET}\\) \u2014 becomes unreliable.<\/li>\n<li><strong>Micropores:<\/strong> in pores narrower than ~2 nm the monolayer concept breaks down because pore filling competes with multilayer adsorption. For strongly microporous materials, report \\(S_{BET}\\) alongside micropore volumes from t-plot or DFT analysis.<\/li>\n<li><strong>Degassing:<\/strong> the sample must be fully degassed before measurement so that all surface is accessible to the adsorbate; residual water or contaminants bias the result low.<\/li>\n<li><strong>STP convention:<\/strong> if you enter the monolayer amount as a gas volume, it must be corrected to STP (0 \u00b0C, 1 atm), where 1 mol occupies 22,414 cm\u00b3. Instruments reporting volumes at other conditions need conversion first \u2014 the same ideal-gas relationships behind the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/gas-density-calculator\/\">gas density<\/a> and <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/molecular-speed-of-a-gas-calculator\/\">molecular speed<\/a> calculators.<\/li>\n<\/ul>\n<p>For quality control, always record the adsorbate, temperature, \\(A_m\\) value, relative-pressure range, and C constant of the BET fit together with \\(S_{BET}\\), since these details determine whether results from different laboratories are comparable.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Calculate the BET specific surface area (m\u00b2\/g) of a powder or porous material from the monolayer capacity, molecular cross-sectional area, and sample mass. Works with mol, mmol, or cm\u00b3 (STP) input.<\/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":[54],"tags":[61],"class_list":["post-66917","post","type-post","status-publish","format-standard","hentry","category-chemistry","tag-bonding"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66917","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=66917"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66917\/revisions"}],"predecessor-version":[{"id":66918,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66917\/revisions\/66918"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66917"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66917"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66917"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}