{"id":59573,"date":"2016-04-05T07:36:07","date_gmt":"2016-04-05T05:36:07","guid":{"rendered":"http:\/\/wpcalc.com\/?p=59573"},"modified":"2026-09-29T14:57:52","modified_gmt":"2026-09-29T11:57:52","slug":"crude-protein","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/chemistry\/crude-protein\/","title":{"rendered":"Crude Protein 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 Crude Protein Percentage<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"59573\" data-favorite-title=\"Crude Protein\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/chemistry\/crude-protein\/\" data-favorite-excerpt=\"Calculate crude protein percentage from Kjeldahl back-titration data. Enter the blank and sample NaOH titre values, NaOH normality, and sample weight.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-biology\">\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\/crude-protein\/\" method=\"POST\" class=\"calculator\" id=\"calculator-59573\" data-post=\"59573\"><fieldset class=\"fieldset-input\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field\" id=\"input-1\"><label for=\"field-1\">Blank titre value (ml)<\/label><input type=\"number\" name=\"blank_titre_value_ml\" id=\"field-1\" aria-describedby=\"calc-info-1\" placeholder=\"e.g. 12.5\" step=\"any\" value=\"12.5\"\/><small id=\"calc-info-1\">Volume of NaOH used in blank titration<\/small><\/div><div class=\"field\" id=\"input-2\"><label for=\"field-2\">Sample titre value (ml)<\/label><input type=\"number\" name=\"sample_titre_value_ml\" id=\"field-2\" aria-describedby=\"calc-info-2\" placeholder=\"e.g. 5.2\" step=\"any\" value=\"5.2\"\/><small id=\"calc-info-2\">Volume of NaOH used for the sample<\/small><\/div><div class=\"field\" id=\"input-3\"><label for=\"field-3\">Normality of NaOH (N)<\/label><input type=\"number\" name=\"normality_of_naoh_n\" id=\"field-3\" aria-describedby=\"calc-info-3\" placeholder=\"e.g. 0.1\" step=\"any\" value=\"0.1\"\/><small id=\"calc-info-3\">Concentration of NaOH solution<\/small><\/div><div class=\"field\" id=\"input-4\"><label for=\"field-4\">Sample weight (g)<\/label><input type=\"number\" name=\"sample_weight_g\" id=\"field-4\" aria-describedby=\"calc-info-4\" placeholder=\"e.g. 0.5\" step=\"any\" value=\"0.5\"\/><small id=\"calc-info-4\">Weight of the feed sample<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"59573\">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>Percentage of Crude Protein<\/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=\"59573\" 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>Crude Protein 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\\[\\text{Crude protein (\\%)}=\\frac{(B-S)\\times N\\times 1.4\\times 6.25}{W}\\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(B\\) \u2014 blank NaOH titre value (mL)<\/li>\n<li>\\(S\\) \u2014 sample NaOH titre value (mL)<\/li>\n<li>\\(N\\) \u2014 normality of NaOH (N)<\/li>\n<li>\\(W\\) \u2014 sample weight (g)<\/li>\n<li>\\(1.4\\) \u2014 factor that converts the titre difference into nitrogen percentage for these units<\/li>\n<li>\\(6.25\\) \u2014 factor that converts nitrogen percentage into crude protein percentage<\/li>\n<\/ul>\n<p>The titre difference represents the acid consumed by ammonia from the sample in this back-titration setup. The formula first estimates nitrogen as a percentage of sample weight, then multiplies it by 6.25 to estimate crude protein.<\/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>Crude Protein \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> A 0.5 g feed sample has a sample NaOH titre of 5.2 mL. The blank titre is 12.5 mL, and the NaOH normality is 0.1 N.<\/p>\n<p>\\[\\text{Crude protein (\\%)}=\\frac{(12.5-5.2)\\times0.1\\times1.4\\times6.25}{0.5}=12.775\\%\\approx12.78\\%\\]<\/p>\n<p><strong>Result:<\/strong> 12.78% crude protein by sample weight.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to use the calculator<\/h2>\n<ol>\n<li>Enter <strong>Blank titre value (ml)<\/strong>: the volume of NaOH used to titrate the blank, which is processed without the sample.<\/li>\n<li>Enter <strong>Sample titre value (ml)<\/strong>: the volume of NaOH used to titrate the sample under the same procedure. For this calculation, it must not exceed the blank titre.<\/li>\n<li>Enter <strong>Normality of NaOH (N)<\/strong>: the concentration of the NaOH titrant in equivalents per litre. Use the standardized normality if it differs from the concentration you intended to prepare.<\/li>\n<li>Enter <strong>Sample weight (g)<\/strong>: the mass of material analyzed, in grams. This value must be greater than zero.<\/li>\n<li>Read <strong>Percentage of Crude Protein<\/strong>. The calculator rounds the result to two decimal places.<\/li>\n<\/ol>\n<h2>What crude protein percentage means<\/h2>\n<p>Crude protein is an estimate based on the nitrogen measured in a sample, rather than a direct measurement of its protein molecules. In the Kjeldahl method, digestion converts much of the sample\u2019s nitrogen to ammonium. Ammonia is then released during distillation and collected for titration. The measured nitrogen is multiplied by a conversion factor to report an estimated protein percentage.<\/p>\n<p>This calculator uses a factor of 6.25, corresponding to an assumed protein nitrogen content of 16%: \\(100\/16=6.25\\). That convention makes results useful for routine comparison of feed and food samples. The number is a mass percentage: for example, 12.78% represents an estimated 12.78 g of crude protein per 100 g of sample on the same weight basis used for the test.<\/p>\n<p>\u201cCrude\u201d matters because Kjeldahl nitrogen may include nitrogen from non-protein compounds. Multiplying all measured nitrogen by 6.25 can therefore give a value higher than the amount of true protein. Some foods and reporting standards also use a protein conversion factor other than 6.25; this calculator does not allow that factor to be changed. For a different aspect of feed composition, use the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/crude-fibre\/\">Crude Fibre Calculator<\/a>.<\/p>\n<h2>Assumptions and practical checks<\/h2>\n<p>The formula assumes a back-titration procedure in which the blank requires more NaOH than the sample. Their difference must correspond to acid neutralized by ammonia from the analyzed portion. Do not use these inputs unchanged for a direct titration, a procedure with a different blank correction, or a method that requires an aliquot or dilution factor: those methods may need a different calculation.<\/p>\n<p>Check that both titre values are nonnegative, that NaOH normality is positive, and that the sample weight is correct. The calculator displays an error when sample weight is zero or negative or when the sample titre exceeds the blank, but its input check does not verify every other physically meaningful condition. A blank and sample titre that are equal produce 0% in the formula; if that is unexpected, review the titration and recorded values.<\/p>\n<p>Report whether the sample weight was measured as received or after drying. A crude protein percentage on an as-received basis is not directly comparable with one on a dry-matter basis. Consistent sample preparation, complete digestion and distillation, a suitable blank, and standardized NaOH all affect the reliability of the result. If preparing NaOH by dilution before standardization, the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/c1v1-c2v2\/\">C1V1 = C2V2 Calculator<\/a> can help plan the dilution; use the verified normality for the protein calculation.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Calculate crude protein percentage from Kjeldahl back-titration data. Enter the blank and sample NaOH titre values, NaOH normality, and sample weight.<\/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":[54],"tags":[60],"class_list":["post-59573","post","type-post","status-publish","format-standard","hentry","category-chemistry","tag-biochemistry"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/59573","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=59573"}],"version-history":[{"count":5,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/59573\/revisions"}],"predecessor-version":[{"id":65578,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/59573\/revisions\/65578"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=59573"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=59573"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=59573"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}