{"id":66664,"date":"2026-10-13T08:31:08","date_gmt":"2026-10-13T05:31:08","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66664"},"modified":"2026-10-13T08:31:08","modified_gmt":"2026-10-13T05:31:08","slug":"ohms-law","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/engineering\/ohms-law\/","title":{"rendered":"Ohm\u2019s Law"},"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\">Enter Any Two Values to Find the Third<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66664\" data-favorite-title=\"Ohm\u2019s Law\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/engineering\/ohms-law\/\" data-favorite-excerpt=\"Calculate voltage, current, resistance, or power using Ohm&#039;s Law. Enter any two known values and the calculator instantly finds the missing quantity.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-electrical\">\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\/ohms-law\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66664\" data-post=\"66664\"><fieldset class=\"fieldset-input\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Voltage<\/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=\"voltage\" id=\"field-1\" aria-describedby=\"calc-unit-1 calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"leave empty if unknown\" min=\"0\" value=\"12\"\/><div class=\"unit\" id=\"calc-unit-1\">V<\/div><small id=\"calc-info-1\">Leave this empty if voltage is the value you want to find<\/small><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-2\">Current<\/label><div class=\"term\">I<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"current\" id=\"field-2\" aria-describedby=\"calc-unit-2 calc-info-2\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"leave empty if unknown\" min=\"0\" value=\"2\"\/><div class=\"unit\" id=\"calc-unit-2\">A<\/div><small id=\"calc-info-2\">Leave this empty if current is the value you want to find<\/small><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-3\">Resistance<\/label><div class=\"term\">R<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"resistance\" id=\"field-3\" aria-describedby=\"calc-unit-3 calc-info-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"leave empty if unknown\" min=\"0\"\/><div class=\"unit\" id=\"calc-unit-3\">\u03a9<\/div><small id=\"calc-info-3\">Leave this empty if resistance is the value you want to find<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66664\">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> Ohm&#039;s Law Results<\/h3><div class=\"result-box\"><div class=\"field-result is-column\" id=\"output-1\"><span class=\"field-title\"><span>Missing Quantity<\/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>Voltage<\/span><span class=\"result-term\">V<\/span><\/span><span class=\"field-value\" id=\"result-2\" data-unit=\"V\"><\/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-3\"><span class=\"field-title\"><span>Current<\/span><span class=\"result-term\">I<\/span><\/span><span class=\"field-value\" id=\"result-3\" data-unit=\"A\"><\/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-4\"><span class=\"field-title\"><span>Resistance<\/span><span class=\"result-term\">R<\/span><\/span><span class=\"field-value\" id=\"result-4\" data-unit=\"\u03a9\"><\/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-5\"><span class=\"field-title\"><span>Power<\/span><span class=\"result-term\">P<\/span><\/span><span class=\"field-value\" id=\"result-5\" data-unit=\"W\"><\/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=\"66664\" 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>Ohm's Law 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\">\\[ V = I \\times R \\quad \\Rightarrow \\quad I = \\frac{V}{R}, \\; R = \\frac{V}{I} \\]<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(V\\) \u2014 voltage across the conductor (volts, V)<\/li>\n<li>\\(I\\) \u2014 current flowing through the conductor (amperes, A)<\/li>\n<li>\\(R\\) \u2014 resistance of the conductor (ohms, \u03a9)<\/li>\n<\/ul>\n<p>The law states that the current through a conductor between two points is directly proportional to the voltage across them and inversely proportional to the resistance between them. Once two of the three quantities are known, the third follows directly.<\/p>\n<p>The calculator also reports the dissipated power, calculated as \\(P = V \\times I\\), which can also be written as \\(P = I^2 R\\) or \\(P = V^2 \/ R\\).<\/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>Ohm's Law \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<p>{content}<\/p>\n<p><strong>Example:<\/strong> a 12 V power supply drives a circuit and you measure a current of 2 A. What is the resistance of the load, and how much power does it dissipate?<\/p>\n<p>\\[ R = \\frac{V}{I} = \\frac{12}{2} = 6 \\; \\Omega \\]<\/p>\n<p>\\[ P = V \\times I = 12 \\times 2 = 24 \\; \\text{W} \\]<\/p>\n<p><strong>Result:<\/strong> resistance is 6 \u03a9 and the circuit dissipates 24 W of power.<\/p>\n<p>{\/content}<\/p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>Enter the two values you know in the <strong>Voltage<\/strong> (V) and <strong>Current<\/strong> (A) fields, or in whichever two of the three fields apply to your problem.<\/li>\n<li>Leave the field for the unknown quantity empty \u2014 the placeholder text \"leave empty if unknown\" reminds you of this.<\/li>\n<li>Check the <strong>Ohm's Law Results<\/strong> panel: the <strong>Missing Quantity<\/strong> row shows which value was calculated and how, and the remaining rows list the full set of values: Voltage, Current, Resistance, and Power.<\/li>\n<li>Enter exactly two values. If all three fields are filled, or only one, the calculator shows an error message instead of a result.<\/li>\n<\/ol>\n<h2>What Is Ohm's Law?<\/h2>\n<p>Ohm's Law, formulated by German physicist Georg Simon Ohm in 1827, is one of the most fundamental relationships in electrical engineering and physics. It describes how voltage, current, and resistance interact in an electrical circuit: push more voltage through a given resistance and more current flows; increase the resistance at a fixed voltage and the current drops.<\/p>\n<p>The law is the working basis for circuit analysis. Whether you are sizing a resistor for an LED, checking whether a wire can carry a load, or troubleshooting why a device draws too much current, you will apply \\(V = IR\\) at some point. The power figure \\(P = V \\times I\\) that the calculator also provides is equally important: it tells you how much energy per second the component converts to heat, which determines whether a resistor, wire, or power supply is rated adequately for the job.<\/p>\n<p>A useful way to interpret the result: if you calculated resistance, the value represents how strongly the load opposes current flow at the given voltage. If you calculated current, the value tells you what the load will draw from the source \u2014 a key number for choosing fuses, power supplies, and cable gauge. If you calculated voltage, the value is the electrical \"pressure\" required to push the given current through the given resistance.<\/p>\n<h2>Assumptions, Limitations, and Practical Tips<\/h2>\n<ul>\n<li><strong>DC and resistive loads only.<\/strong> Ohm's Law in this simple form applies to direct current and purely resistive components. For AC circuits with reactive elements, impedance replaces resistance and phase angles come into play \u2014 see the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/real-reactive-power\/\">Real and Reactive Power calculator<\/a> for those cases.<\/li>\n<li><strong>Linear behavior assumed.<\/strong> The law holds for ohmic (linear) components. Diodes, lamps with filaments, and semiconductors have a nonlinear voltage\u2013current relationship, so a single resistance value does not describe them across different operating points.<\/li>\n<li><strong>Temperature effects.<\/strong> Real resistors change value with temperature. A calculation made at room temperature may not hold when a component heats up under load.<\/li>\n<li><strong>Division by zero.<\/strong> To calculate current, resistance must be greater than zero; to calculate resistance, current must be greater than zero. The calculator rejects these inputs with an error message.<\/li>\n<li><strong>No negative values.<\/strong> Voltage, current, and resistance cannot be negative in this context; negative inputs are rejected. In real circuits, current direction matters, but magnitude calculations are what this tool provides.<\/li>\n<\/ul>\n<p>When a circuit contains several resistors, reduce them to a single equivalent value first \u2014 the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/parallel-resistance\/\">Parallel Resistance calculator<\/a> handles the parallel case. If you are designing in electronics, the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/zener-diode\/\">Zener Diode Resistor calculator<\/a> applies Ohm's Law to size the series resistor in a voltage regulator, and the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/wire-gauge\/\">Wire Gauge calculator<\/a> helps you pick a conductor that safely carries the current you just calculated.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Calculate voltage, current, resistance, or power using Ohm's Law. Enter any two known values and the calculator instantly finds the missing quantity.<\/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":[4],"tags":[94],"class_list":["post-66664","post","type-post","status-publish","format-standard","hentry","category-engineering","tag-circuits"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66664","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=66664"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66664\/revisions"}],"predecessor-version":[{"id":66665,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66664\/revisions\/66665"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66664"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66664"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66664"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}