{"id":66482,"date":"2026-10-06T17:20:49","date_gmt":"2026-10-06T14:20:49","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66482"},"modified":"2026-10-06T17:20:49","modified_gmt":"2026-10-06T14:20:49","slug":"equilibrium-constant-calculator","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/chemistry\/equilibrium-constant-calculator\/","title":{"rendered":"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 Kc from Equilibrium Concentrations<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66482\" data-favorite-title=\"Equilibrium Constant\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/chemistry\/equilibrium-constant-calculator\/\" data-favorite-excerpt=\"Calculate the equilibrium constant Kc from the equilibrium concentrations of reactants and products. Enter the stoichiometric coefficients and concentrations from your balanced equation to get Kc, 1\/Kc, and whether the reaction is product- or reactant-favoured.\" 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\/equilibrium-constant-calculator\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66482\" data-post=\"66482\"><fieldset class=\"fieldset-input is-1\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field\" id=\"input-1\"><label for=\"field-1\">Number of Reactants<\/label><div class=\"grid grid-cols-1\"><select id=\"field-1\" name=\"number_of_reactants\"><option value=\"r1\">1 reactant<\/option><option value=\"r2\" selected>2 reactants<\/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><div class=\"field\" id=\"input-2\"><label for=\"field-2\">Number of Products<\/label><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"number_of_products\"><option value=\"p1\">1 product<\/option><option value=\"p2\" selected>2 products<\/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><div class=\"is-single field\" id=\"input-3\"><span class=\"font-semibold\">Reactants (a A + b B \u21cc)<\/span><\/div><div class=\"field has-term\" id=\"input-4\"><label for=\"field-4\">Coefficient of A (a)<\/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=\"coefficient_of_a_a\" id=\"field-4\" aria-describedby=\"calc-info-4\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 1\" min=\"1\" value=\"1\"\/><small id=\"calc-info-4\">Stoichiometric coefficient from the balanced equation<\/small><\/div><div class=\"field has-term\" id=\"input-5\"><label for=\"field-5\">Concentration of A [A]<\/label><div class=\"term\">[A]<\/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=\"concentration_of_a_a\" id=\"field-5\" aria-describedby=\"calc-info-5\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.5\" min=\"0\" value=\"0.5\"\/><div class=\"grid grid-cols-1\"><select id=\"field-6\" name=\"unit\" aria-label=\"Unit\"><option value=\"mol_l\" selected>mol\/L<\/option><option value=\"mmol_l\">mmol\/L<\/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\">Equilibrium concentration of reactant A<\/small><\/div><div class=\"field has-term\" id=\"input-6\" hidden><label for=\"field-7\">Coefficient of B (b)<\/label><div class=\"term\">b<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"coefficient_of_b_b\" id=\"field-7\" aria-describedby=\"calc-info-7\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 1\" min=\"1\" value=\"1\"\/><small id=\"calc-info-7\">Stoichiometric coefficient from the balanced equation<\/small><\/div><div class=\"field has-term\" id=\"input-7\" hidden><label for=\"field-8\">Concentration of B [B]<\/label><div class=\"term\">[B]<\/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=\"concentration_of_b_b\" id=\"field-8\" aria-describedby=\"calc-info-8\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.3\" min=\"0\" value=\"0.3\"\/><div class=\"grid grid-cols-1\"><select id=\"field-9\" name=\"unit\" aria-label=\"Unit\"><option value=\"mol_l\" selected>mol\/L<\/option><option value=\"mmol_l\">mmol\/L<\/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-8\">Equilibrium concentration of reactant B<\/small><\/div><div class=\"is-single field\" id=\"input-8\"><span class=\"font-semibold\">Products (\u21cc c C + d D)<\/span><\/div><div class=\"field has-term\" id=\"input-9\"><label for=\"field-11\">Coefficient of C (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><input type=\"text\" name=\"coefficient_of_c_c\" id=\"field-11\" aria-describedby=\"calc-info-11\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 1\" min=\"1\" value=\"1\"\/><small id=\"calc-info-11\">Stoichiometric coefficient from the balanced equation<\/small><\/div><div class=\"field has-term\" id=\"input-10\"><label for=\"field-12\">Concentration of C [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=\"concentration_of_c_c\" id=\"field-12\" aria-describedby=\"calc-info-12\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.4\" min=\"0\" value=\"0.4\"\/><div class=\"grid grid-cols-1\"><select id=\"field-13\" name=\"unit\" aria-label=\"Unit\"><option value=\"mol_l\" selected>mol\/L<\/option><option value=\"mmol_l\">mmol\/L<\/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-12\">Equilibrium concentration of product C<\/small><\/div><div class=\"field has-term\" id=\"input-11\" hidden><label for=\"field-14\">Coefficient of D (d)<\/label><div class=\"term\">d<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"coefficient_of_d_d\" id=\"field-14\" aria-describedby=\"calc-info-14\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 1\" min=\"1\" value=\"1\"\/><small id=\"calc-info-14\">Stoichiometric coefficient from the balanced equation<\/small><\/div><div class=\"field has-term\" id=\"input-12\" hidden><label for=\"field-15\">Concentration of D [D]<\/label><div class=\"term\">[D]<\/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=\"concentration_of_d_d\" id=\"field-15\" aria-describedby=\"calc-info-15\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.2\" min=\"0\" value=\"0.2\"\/><div class=\"grid grid-cols-1\"><select id=\"field-16\" name=\"unit\" aria-label=\"Unit\"><option value=\"mol_l\" selected>mol\/L<\/option><option value=\"mmol_l\">mmol\/L<\/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-15\">Equilibrium concentration of product D<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66482\">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\" id=\"output-1\"><span class=\"field-title\"><span>Concentration Equilibrium Constant<\/span><span class=\"result-term\">Kc<\/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>Equilibrium Constant of the Reverse Reaction<\/span><span class=\"result-term\">1\/Kc<\/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>Position of Equilibrium<\/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=\"66482\" 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>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\\[ K_c = \\frac{[C]^c\\,[D]^d}{[A]^a\\,[B]^b} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(K_c\\) \u2014 concentration equilibrium constant (dimensionless)<\/li>\n<li>\\([A]\\), \\([B]\\) \u2014 equilibrium concentrations of the reactants (mol\/L)<\/li>\n<li>\\([C]\\), \\([D]\\) \u2014 equilibrium concentrations of the products (mol\/L)<\/li>\n<li>\\(a\\), \\(b\\), \\(c\\), \\(d\\) \u2014 stoichiometric coefficients from the balanced equation \\(aA + bB \\rightleftharpoons cC + dD\\)<\/li>\n<\/ul>\n<p>The formula states that for a reversible reaction at equilibrium, the product of the product concentrations (each raised to its coefficient) divided by the product of the reactant concentrations (each raised to its coefficient) is a constant at a given temperature. If a species is absent, its term simply drops out of the expression.<\/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>Equilibrium Constant \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> for the reaction \\(A + B \\rightleftharpoons C + D\\) (all coefficients equal to 1), the equilibrium concentrations are \\([A] = 0.5\\ \\text{mol\/L}\\), \\([B] = 0.3\\ \\text{mol\/L}\\), \\([C] = 0.4\\ \\text{mol\/L}\\) and \\([D] = 0.2\\ \\text{mol\/L}\\).<\/p>\n<p>\\[ K_c = \\frac{[C]^1[D]^1}{[A]^1[B]^1} = \\frac{0.4 \\times 0.2}{0.5 \\times 0.3} = \\frac{0.08}{0.15} \\approx 0.5333 \\]<\/p>\n<p>\\[ \\frac{1}{K_c} = \\frac{1}{0.5333} \\approx 1.875 \\]<\/p>\n<p><strong>Result:<\/strong> \\(K_c \\approx 0.5333\\); since \\(K_c &lt; 1\\), the equilibrium mixture is dominated by reactants. The reverse reaction has \\(K_c \\approx 1.875\\).<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>Start with a <strong>balanced chemical equation<\/strong>. If you need help balancing one, use the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/balancing-chemical-equations\/\">Chemical Equation Balancer<\/a> first.<\/li>\n<li>In <strong>Number of Reactants<\/strong>, select \"1 reactant\" or \"2 reactants\" depending on how many species appear on the left side of your equation. Do the same for <strong>Number of Products<\/strong>.<\/li>\n<li>Enter the <strong>Coefficient of A (a)<\/strong> and the <strong>Concentration of A [A]<\/strong> with its unit (mol\/L or mmol\/L) for the first reactant. If you selected 2 reactants, fill in <strong>Coefficient of B (b)<\/strong> and <strong>Concentration of B [B]<\/strong> as well.<\/li>\n<li>Enter the coefficients and equilibrium concentrations of the products: <strong>Coefficient of C (c)<\/strong>, <strong>Concentration of C [C]<\/strong>, and, if applicable, <strong>Coefficient of D (d)<\/strong> and <strong>Concentration of D [D]<\/strong>.<\/li>\n<li>Read the results: the <strong>Concentration Equilibrium Constant<\/strong> \\(K_c\\), the <strong>Equilibrium Constant of the Reverse Reaction<\/strong> \\(1\/K_c\\), and the <strong>Position of Equilibrium<\/strong>, which tells you whether products or reactants dominate.<\/li>\n<\/ol>\n<h2>What Is the Equilibrium Constant?<\/h2>\n<p>A reversible reaction does not stop when reactants and products reach equal amounts \u2014 it stops changing when the forward and reverse rates become equal. At that point, the <em>equilibrium<\/em> composition is fixed, and the ratio defined by the equilibrium expression is a constant characteristic of the reaction at that temperature. This constant, \\(K_c\\), tells you how far a reaction proceeds toward products before the net change ceases.<\/p>\n<p>The value of \\(K_c\\) is a measure of the position of equilibrium. A large \\(K_c\\) (roughly above \\(10^3\\)) means the reaction goes almost to completion: at equilibrium, almost everything has been converted to products. A small \\(K_c\\) (roughly below \\(10^{-3}\\)) means very little product forms. Values in between indicate a genuine mixture of reactants and products at equilibrium. Note that \\(K_c\\) says nothing about how <em>fast<\/em> equilibrium is reached \u2014 that is a question of reaction rate, covered by the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/arrhenius-equation-2\/\">Arrhenius Equation<\/a>.<\/p>\n<p>Every reaction has a matching reverse reaction whose equilibrium constant is the reciprocal: \\(K_{reverse} = 1\/K_{forward}\\). This is why the calculator also reports \\(1\/K_c\\) \u2014 useful when you are asked about the reverse direction or want to check consistency between tabulated values.<\/p>\n<p>\\(K_c\\) is temperature-dependent. Changing concentration, pressure or volume shifts the equilibrium position (Le Chatelier's principle) but never changes \\(K_c\\); only a change in temperature does. When comparing values from different sources, always check they refer to the same temperature.<\/p>\n<h2>Assumptions, Limitations and Practical Tips<\/h2>\n<ul>\n<li><strong>Use equilibrium concentrations, not starting ones.<\/strong> The calculator expects the concentrations that exist <em>at equilibrium<\/em>. If you are given initial concentrations and one equilibrium value, set up an ICE table (Initial, Change, Equilibrium) first to work out the remaining equilibrium concentrations.<\/li>\n<li><strong>The equation must be balanced.<\/strong> The coefficients you enter are used as exponents, so an unbalanced equation gives a wrong \\(K_c\\).<\/li>\n<li><strong>Pure solids and liquids are excluded.<\/strong> Only dissolved species (and gases, for \\(K_p\\)) appear in the equilibrium expression. If your reaction involves a solid or pure liquid, omit it from the count of reactants or products.<\/li>\n<li><strong>The calculator handles up to 2 reactants and 2 products.<\/strong> For reactions with more species, apply the same pattern by hand: every product concentration to its coefficient power in the numerator, every reactant concentration to its coefficient power in the denominator.<\/li>\n<li><strong>Units are converted automatically.<\/strong> Concentrations entered in mmol\/L are converted to mol\/L before the calculation, so all terms must simply be in the same unit system for the result to be meaningful.<\/li>\n<li><strong>\\(K_c\\) is formally dimensionless.<\/strong> Although the underlying concentrations carry units, thermodynamic equilibrium constants are defined in terms of activities, so the result is treated as a pure number.<\/li>\n<li>Equilibrium problems often involve solutions prepared from molar masses. To convert between mass and concentration, the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/molarity-calculator\/\">Molarity<\/a> and <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/molality-calculator\/\">Molality<\/a> calculators can help.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Calculate the equilibrium constant Kc from the equilibrium concentrations of reactants and products. Enter the stoichiometric coefficients and concentrations from your balanced equation to get Kc, 1\/Kc, and whether the reaction is product- or reactant-favoured.<\/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-66482","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\/66482","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=66482"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66482\/revisions"}],"predecessor-version":[{"id":66483,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66482\/revisions\/66483"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66482"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66482"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66482"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}