{"id":66909,"date":"2026-10-13T10:12:09","date_gmt":"2026-10-13T07:12:09","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66909"},"modified":"2026-10-13T10:12:09","modified_gmt":"2026-10-13T07:12:09","slug":"electrochemical-equilibrium-constant-calculator","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/chemistry\/electrochemical-equilibrium-constant-calculator\/","title":{"rendered":"Electrochemical Equilibrium Constant 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 K from the Standard Cell Potential<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66909\" data-favorite-title=\"Electrochemical Equilibrium Constant\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/chemistry\/electrochemical-equilibrium-constant-calculator\/\" data-favorite-excerpt=\"Enter the standard cell potential E\u00b0cell, the number of electrons transferred n, and the temperature to find the equilibrium constant K of a redox reaction from \u0394G\u00b0 = \u2212nFE\u00b0 = \u2212RT ln K.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-chemistry-1\">\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\/electrochemical-equilibrium-constant-calculator\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66909\" data-post=\"66909\"><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\">Standard Cell Potential (E\u00b0cell)<\/label><div class=\"term\">E\u00b0cell<\/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=\"number\" name=\"standard_cell_potential_ecell\" id=\"field-1\" aria-describedby=\"calc-info-1\" placeholder=\"e.g. 1.10\" step=\"any\" value=\"1.1\"\/><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"unit\" aria-label=\"Unit\"><option value=\"V\" selected>V<\/option><option value=\"mV\">mV<\/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\">Difference of the standard reduction potentials: E\u00b0cell = E\u00b0cathode \u2212 E\u00b0anode. Negative values are allowed and simply give K &lt; 1.<\/small><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-3\">Electrons Transferred (n)<\/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=\"electrons_transferred_n\" id=\"field-3\" aria-describedby=\"calc-info-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 2\" min=\"0\" value=\"2\"\/><small id=\"calc-info-3\">Number of electrons exchanged in the balanced redox reaction (e.g. 2 for Zn + Cu\u00b2\u207a \u2192 Zn\u00b2\u207a + Cu).<\/small><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-4\">Temperature (T)<\/label><div class=\"term\">T<\/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=\"number\" name=\"temperature_t\" id=\"field-4\" aria-describedby=\"calc-info-4\" placeholder=\"e.g. 25\" step=\"any\" value=\"25\"\/><div class=\"grid grid-cols-1\"><select id=\"field-5\" name=\"unit\" aria-label=\"Unit\"><option value=\"C\" selected>\u00b0C<\/option><option value=\"K\">K<\/option><option value=\"F\">\u00b0F<\/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-4\">Temperature of the cell. 25 \u00b0C (298.15 K) is the standard reference for tabulated E\u00b0 values.<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66909\">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> Equilibrium Constant Results<\/h3><div class=\"result-box\"><div class=\"field-result is-column\" id=\"output-1\"><span class=\"field-title\"><span>Equilibrium Constant (K)<\/span><span class=\"result-term\">K<\/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>log\u2081\u2080 K<\/span><span class=\"result-term\">log K<\/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 This Calculation<\/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=\"66909\" 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>Electrochemical Equilibrium Constant 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\\[ \\ln K = \\frac{nFE^\\circ_{cell}}{RT} \\quad \\Leftrightarrow \\quad \\log_{10} K = \\frac{nFE^\\circ_{cell}}{2.303\\,RT} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(K\\) \u2014 equilibrium constant of the redox reaction (dimensionless)<\/li>\n<li>\\(n\\) \u2014 number of electrons transferred in the balanced reaction<\/li>\n<li>\\(F\\) \u2014 Faraday constant, 96 485.33212 C\/mol<\/li>\n<li>\\(E^\\circ_{cell}\\) \u2014 standard cell potential in volts (V)<\/li>\n<li>\\(R\\) \u2014 gas constant, 8.314462618 J\/(mol\u00b7K)<\/li>\n<li>\\(T\\) \u2014 absolute temperature in kelvin (K)<\/li>\n<\/ul>\n<p>The formula combines two expressions for the standard Gibbs free energy change, \\(\\Delta G^\\circ = -nFE^\\circ_{cell}\\) and \\(\\Delta G^\\circ = -RT\\ln K\\). Equating them shows that the cell voltage directly measures how far the equilibrium lies toward products.<\/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>Electrochemical Equilibrium Constant \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> the Daniell cell, Zn(s) + Cu\u00b2\u207a(aq) \u2192 Zn\u00b2\u207a(aq) + Cu(s), has E\u00b0cell = 1.10 V and transfers n = 2 electrons at 25 \u00b0C (298.15 K).<\/p>\n<p>\\[ \\log_{10} K = \\frac{nFE^\\circ_{cell}}{2.303\\,RT} = \\frac{2 \\times 96485.33 \\times 1.10}{2.303 \\times 8.3145 \\times 298.15} \\approx 37.19 \\]<\/p>\n<p><strong>Result:<\/strong> \\(K = 10^{37.19} \\approx 1.55 \\times 10^{37}\\). The equilibrium lies overwhelmingly on the product side \u2014 the reaction goes essentially to completion.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>Enter the <strong>Standard Cell Potential (E\u00b0cell)<\/strong> as E\u00b0cathode \u2212 E\u00b0anode, and choose V or mV as the unit. Negative values are accepted and simply give K &lt; 1.<\/li>\n<li>Enter the <strong>Electrons Transferred (n)<\/strong> \u2014 the number of electrons cancelled when the two half-reactions are combined (e.g. 2 for Zn + Cu\u00b2\u207a \u2192 Zn\u00b2\u207a + Cu).<\/li>\n<li>Enter the <strong>Temperature (T)<\/strong> and select \u00b0C, K, or \u00b0F. Tabulated standard potentials refer to 25 \u00b0C (298.15 K).<\/li>\n<li>Read the results: the equilibrium constant K (in scientific notation), the value of log\u2081\u2080K, and a step-by-step calculation showing the substitution of constants.<\/li>\n<\/ol>\n<h2>What Is the Electrochemical Equilibrium Constant?<\/h2>\n<p>Every redox reaction has an equilibrium constant that tells you how far the reaction proceeds before reaching equilibrium. For the Daniell cell, K \u2248 10\u00b3\u2077 means that zinc metal reduces copper ions essentially completely. Measuring such huge constants chemically is hopeless \u2014 concentrations of the losing species become immeasurably small \u2014 but the cell potential gives them indirectly and with great sensitivity.<\/p>\n<p>The link is the Gibbs free energy. A cell does electrical work equal to \\(nFE^\\circ_{cell}\\) per mole of reaction, and the same \\(\\Delta G^\\circ\\) also fixes K through \\(\\Delta G^\\circ = -RT\\ln K\\). Because \\(F\/RT\\) is a very large number (about 38.9 V\u207b\u00b9 at 25 \u00b0C per unit of ln), each volt of cell potential corresponds to many tens of powers of ten in K. A change of only 59.2 mV in E\u00b0cell shifts log\u2081\u2080K by one full unit per electron transferred.<\/p>\n<p>Interpreting the result is straightforward: a positive E\u00b0cell means \\(\\Delta G^\\circ &lt; 0\\) and K &gt; 1 (products favored under standard conditions); E\u00b0cell = 0 gives K = 1; a negative E\u00b0cell gives K &lt; 1 (reactants favored). When |log\u2081\u2080K| climbs above 30 or so, the reaction is so one-sided that it is experimentally indistinguishable from complete \u2014 the calculator will show K as a power of ten rather than a plain number.<\/p>\n<p>To get E\u00b0cell itself, look up the two standard reduction potentials and subtract, or use our <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/standard-cell-potential-calculator\/\">Standard Cell Potential calculator<\/a>. The same activity-based logic behind this K also governs the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/solubility-product-ksp-calculator\/\">solubility product Ksp<\/a>, and the free-energy bookkeeping parallels <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/hesss-law-calculator\/\">Hess's Law<\/a>.<\/p>\n<h2>Assumptions, Limitations and Practical Tips<\/h2>\n<ul>\n<li><strong>Standard conditions:<\/strong> the formula assumes all species are at unit activity (1 M for solutes, 1 bar for gases). Real concentrations differ from activities at anything but dilute conditions \u2014 see the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/debye-huckel-activity-coefficient-calculator\/\">Debye\u2013H\u00fcckel Activity Coefficient calculator<\/a> for corrections in ionic solutions.<\/li>\n<li><strong>Balanced reaction required:<\/strong> n must come from the fully balanced equation. Multiply half-reactions to cancel electrons before counting them; a wrong n shifts log K proportionally.<\/li>\n<li><strong>Temperature consistency:<\/strong> tabulated E\u00b0 values are measured at 25 \u00b0C. If you enter a different temperature, the calculator applies the formal relation correctly, but the true E\u00b0cell also changes slightly with T, so treat non-25 \u00b0C results as approximations.<\/li>\n<li><strong>Significant figures:<\/strong> standard potentials are typically quoted to 2\u20133 decimal places, so log K is rarely meaningful beyond 2\u20133 significant figures, and K itself beyond the leading digit of the mantissa.<\/li>\n<li><strong>K is dimensionless:<\/strong> it is the thermodynamic constant based on activities, not the quotient of molar concentrations. For dilute solutions the two nearly coincide.<\/li>\n<li><strong>Non-integer n:<\/strong> the calculator accepts fractional n (e.g. per mole of a chosen formula unit), but then K refers to the reaction written in that specific way \u2014 changing how you divide the equation changes n and K together.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Enter the standard cell potential E\u00b0cell, the number of electrons transferred n, and the temperature to find the equilibrium constant K of a redox reaction from \u0394G\u00b0 = \u2212nFE\u00b0 = \u2212RT ln K.<\/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":[57],"class_list":["post-66909","post","type-post","status-publish","format-standard","hentry","category-chemistry","tag-reactions"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66909","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=66909"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66909\/revisions"}],"predecessor-version":[{"id":66910,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66909\/revisions\/66910"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66909"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66909"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66909"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}