{"id":67321,"date":"2026-10-21T09:52:45","date_gmt":"2026-10-21T06:52:45","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=67321"},"modified":"2026-10-26T10:02:30","modified_gmt":"2026-10-26T07:02:30","slug":"watts-to-amps-calculator-and-amps-to-watts","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/engineering\/watts-to-amps-calculator-and-amps-to-watts\/","title":{"rendered":"Watts to Amps Calculator \u2013 and kW to Amps"},"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\">Convert Watts, kW or kVA to Amps \u2014 or Amps Back to Watts<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"67321\" data-favorite-title=\"Watts to Amps\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/engineering\/watts-to-amps-calculator-and-amps-to-watts\/\" data-favorite-excerpt=\"Convert watts to amps or amps to watts for DC, single-phase AC and three-phase AC circuits. Enter power, voltage and power factor to get current, apparent power and suggested breaker size.\" 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\/watts-to-amps-calculator-and-amps-to-watts\/\" method=\"POST\" class=\"calculator\" id=\"calculator-67321\" data-post=\"67321\"><fieldset class=\"fieldset-input is-2\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field\" id=\"input-1\"><label for=\"field-1\">Convert<\/label><div class=\"grid grid-cols-1\"><select id=\"field-1\" name=\"convert\"><option value=\"amps\" selected>Watts \u2192 Amps<\/option><option value=\"watts\">Amps \u2192 Watts<\/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\">Circuit type<\/label><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"circuit_type\"><option value=\"dc\">DC<\/option><option value=\"ac1\" selected>AC single phase<\/option><option value=\"ac3ll\">AC three phase (line-to-line)<\/option><option value=\"ac3ln\">AC three phase (line-to-neutral)<\/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 has-term\" id=\"input-3\"><label for=\"field-3\">Power (P)<\/label><div class=\"term\">P<\/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=\"power_p\" id=\"field-3\" aria-describedby=\"calc-info-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 1200\" min=\"0\" value=\"1200\"\/><div class=\"grid grid-cols-1\"><select id=\"field-4\" name=\"power_unit\" aria-label=\"Power unit\"><option value=\"w\" selected>W<\/option><option value=\"kw\">kW<\/option><option value=\"kva\">kVA<\/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\">Power to convert into current; kVA is apparent power (the power factor is not used)<\/small><\/div><div class=\"field has-term\" id=\"input-4\" hidden><label for=\"field-5\">Current (I)<\/label><div class=\"term\">I<\/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=\"current_i\" id=\"field-5\" aria-describedby=\"calc-info-5\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 10\" min=\"0\" value=\"10\"\/><div class=\"grid grid-cols-1\"><select id=\"field-6\" name=\"current_unit\" aria-label=\"Current unit\"><option value=\"a\" selected>A<\/option><option value=\"ma\">mA<\/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\">Current to convert into power<\/small><\/div><div class=\"field\" id=\"input-5\"><label for=\"field-7\">Voltage (V)<\/label><div class=\"grid grid-cols-1\"><select id=\"field-7\" name=\"voltage_v\"><option value=\"v12\">12 V<\/option><option value=\"v24\">24 V<\/option><option value=\"v120\" selected>120 V<\/option><option value=\"v208\">208 V<\/option><option value=\"v230\">230 V<\/option><option value=\"v240\">240 V<\/option><option value=\"v480\">480 V<\/option><option value=\"custom\">Custom\u2026<\/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 has-term\" id=\"input-6\" hidden><label for=\"field-8\">Custom voltage (V)<\/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=\"custom_voltage_v\" id=\"field-8\" aria-describedby=\"calc-unit-8 calc-info-8\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 400\" min=\"0\" value=\"120\"\/><div class=\"unit\" id=\"calc-unit-8\">V<\/div><small id=\"calc-info-8\">Line-to-line voltage for the three-phase line-to-line option; otherwise the voltage you measure<\/small><\/div><div class=\"field has-term\" id=\"input-7\"><label for=\"field-9\">Power factor (PF)<\/label><div class=\"term\">PF<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"power_factor_pf\" id=\"field-9\" aria-describedby=\"calc-info-9\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 0.85\" min=\"0.05\" max=\"1\" value=\"1\"\/><small id=\"calc-info-9\">1.0 for resistive loads (heaters, incandescent lamps); typically 0.8\u20130.95 for motors and other inductive loads<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"67321\">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> Conversion Results<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Current (I)<\/span><span class=\"result-term\">I<\/span><\/span><span class=\"field-value\" id=\"result-1\" 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-2\"><span class=\"field-title\"><span>Power (P)<\/span><span class=\"result-term\">P<\/span><\/span><span class=\"field-value\" id=\"result-2\" 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 class=\"field-result\" id=\"output-3\"><span class=\"field-title\"><span>Active Power<\/span><\/span><span class=\"field-value\" id=\"result-3\" data-unit=\"kW\"><\/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>Apparent Power<\/span><\/span><span class=\"field-value\" id=\"result-4\" data-unit=\"kVA\"><\/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-5\"><span class=\"field-title\"><span>Same Load at Other Voltages<\/span><\/span><span class=\"field-value\" id=\"result-5\"><\/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-6\"><span class=\"field-title\"><span>Formula and Breaker Sizing<\/span><\/span><span class=\"field-value\" id=\"result-6\"><\/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-7\"><span class=\"field-title\"><span>Current in Each Circuit Type<\/span><\/span><span class=\"field-value\" id=\"result-7\"><\/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-8\"><span class=\"field-title\"><span>kW to Amps Quick Table<\/span><\/span><span class=\"field-value\" id=\"result-8\"><\/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=\"67321\" 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>Watts to Amps 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\\[ I = \\frac{P}{k \\times PF \\times V} \\qquad \\text{and, in reverse,} \\qquad P = k \\times PF \\times V \\times I \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(I\\) \u2014 current in amperes (A)<\/li>\n<li>\\(P\\) \u2014 active power in watts (W)<\/li>\n<li>\\(V\\) \u2014 voltage in volts (V): line-to-line for the three-phase line-to-line case, line-to-neutral otherwise<\/li>\n<li>\\(PF\\) \u2014 power factor (1.0 for DC and purely resistive loads)<\/li>\n<li>\\(k\\) \u2014 topology factor: \\(k = 1\\) for DC and single-phase AC, \\(k = \\sqrt{3} \\approx 1.732\\) for three-phase with line-to-line voltage, \\(k = 3\\) for three-phase with line-to-neutral voltage<\/li>\n<\/ul>\n<p>The two formulas express the same relationship from opposite directions: current is power divided by voltage (and, for AC, by power factor and the topology factor), while power is current multiplied by the same quantities. The relationship \\(P = V \\times I\\) is a direct consequence of <a href=\"https:\/\/wpcalc.com\/en\/engineering\/ohms-law\/\">Ohm's Law<\/a>.<\/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>Watts to Amps \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> a 1200 W resistive heater runs on a single-phase 120 V AC circuit with a power factor of 1.0 (the calculator's default values).<\/p>\n<p>\\[ I = \\frac{P}{PF \\times V} = \\frac{1200}{1.0 \\times 120} = 10 \\ \\text{A} \\]<\/p>\n<p><strong>Result:<\/strong> the heater draws 10 A. The apparent power is \\(S = V \\times I = 120 \\times 10 = 1200\\ \\text{VA} = 1.2\\ \\text{kVA}\\). Because a continuous load may use only 80% of a breaker's rating, a 10 A load needs a breaker of at least \\(10 \/ 0.8 = 12.5\\ \\text{A}\\), so the next standard size is 15 A.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to use the calculator<\/h2>\n<ol>\n<li>In the <strong>Convert<\/strong> dropdown choose the direction: <em>Watts \u2192 Amps<\/em> or <em>Amps \u2192 Watts<\/em>. Only the relevant input field is shown.<\/li>\n<li>Select the <strong>Circuit type<\/strong>: <em>DC<\/em>, <em>AC single phase<\/em>, or three-phase AC using either the <em>line-to-line<\/em> or <em>line-to-neutral<\/em> voltage. This controls the topology factor \\(k\\) and whether the power factor is used.<\/li>\n<li>Enter the known quantity: <strong>Power (P)<\/strong> in W or kW, or <strong>Current (I)<\/strong> in A or mA.<\/li>\n<li>Set the <strong>Voltage (V)<\/strong> from the list of common system voltages, or pick <em>Custom\u2026<\/em> and type your own value in the <strong>Custom voltage (V)<\/strong> field. For three-phase line-to-line, enter the line-to-line voltage (e.g. 400 V, not 230 V).<\/li>\n<li>For AC circuits, enter the <strong>Power factor (PF)<\/strong> between 0 and 1. Use 1.0 for heaters and incandescent lamps, typically 0.8\u20130.95 for motors and other inductive loads.<\/li>\n<\/ol>\n<p>Read the result, along with apparent power in kVA, a table showing the same load at other common voltages, and a suggested breaker size based on the 125% rule for continuous loads.<\/p>\n<h2>What the conversion means<\/h2>\n<p>Watts measure power \u2014 the rate at which electrical energy is consumed \u2014 while amperes measure current, the flow of charge through the conductors. For a DC or single-phase resistive circuit the link is simply \\(P = V \\times I\\), which is the rearrangement of \\(I = P \/ V\\): at a fixed voltage, more watts always mean more amps. The conversion matters in practice because wiring, breakers, plugs and fuses are rated in amps, while appliances and nameplates are usually labeled in watts.<\/p>\n<p>On AC circuits two extra factors appear. First, the <em>power factor<\/em>: inductive loads such as motors, transformers and fluorescent ballasts draw current that is partly out of phase with the voltage, so only the fraction \\(PF\\) of the voltage\u2013current product becomes useful power. The remaining portion is the reactive power, and the total product \\(S = V \\times I\\) is the <em>apparent power<\/em> in volt-amperes. That is why a 1200 W motor with \\(PF = 0.8\\) draws more current than a 1200 W heater at the same voltage.<\/p>\n<p>Three-phase systems distribute power over three conductors, adding the factor \\(\\sqrt{3}\\) (line-to-line) or 3 (line-to-neutral) to the formulas. Be consistent with which voltage you enter: 400 V line-to-line corresponds to 230 V line-to-neutral, and mixing the two changes the result by exactly \\(\\sqrt{3}\\).<\/p>\n<p>The suggested breaker size follows NEC 210.20(A): a continuous load (on for 3 hours or more) must not exceed 80% of the breaker rating, so the breaker must be at least 125% of the load current. For a full sizing workflow including conductor ampacity, see the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/circuit-breaker-size\/\">Circuit Breaker Size calculator<\/a>.<\/p>\n<h2>Common watts to amps conversions<\/h2>\n<p>Reference values for single-phase AC with \\(PF = 1\\) (a resistive load):<\/p>\n<table>\n<thead>\n<tr>\n<th>Power<\/th>\n<th>Current at 120 V<\/th>\n<th>Current at 230 V<\/th>\n<th>Current at 240 V<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>300 W<\/td>\n<td>2.50 A<\/td>\n<td>1.30 A<\/td>\n<td>1.25 A<\/td>\n<\/tr>\n<tr>\n<td>600 W<\/td>\n<td>5.00 A<\/td>\n<td>2.61 A<\/td>\n<td>2.50 A<\/td>\n<\/tr>\n<tr>\n<td>1200 W<\/td>\n<td>10.00 A<\/td>\n<td>5.22 A<\/td>\n<td>5.00 A<\/td>\n<\/tr>\n<tr>\n<td>1800 W<\/td>\n<td>15.00 A<\/td>\n<td>7.83 A<\/td>\n<td>7.50 A<\/td>\n<\/tr>\n<tr>\n<td>2400 W<\/td>\n<td>20.00 A<\/td>\n<td>10.43 A<\/td>\n<td>10.00 A<\/td>\n<\/tr>\n<tr>\n<td>3600 W<\/td>\n<td>30.00 A<\/td>\n<td>15.65 A<\/td>\n<td>15.00 A<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Assumptions, limitations and practical tips<\/h2>\n<ul>\n<li>The calculation assumes steady-state operation at a constant voltage. Motor starting (inrush) current can be 5\u20137 times the running current, so size circuits for inrush, not just the computed value.<\/li>\n<li>Nameplate power is often the <em>output<\/em> or rated power; the electrical input may be higher due to efficiency losses. Use the input power (or the nameplate current, if given) for circuit sizing.<\/li>\n<li>The voltages used must be RMS values, and the power factor must correspond to the actual load, not an assumed default. A small error in \\(PF\\) shifts the current proportionally \u2014 you can estimate it with the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/power-factor-correction\/\">Power Factor Correction calculator<\/a>.<\/li>\n<li>For long cable runs, the current also causes a <a href=\"https:\/\/wpcalc.com\/en\/engineering\/electrical-voltage-drop\/\">voltage drop<\/a> along the conductors; check it separately, and choose the conductor with the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/wire-gauge\/\">Wire Gauge calculator<\/a>.<\/li>\n<li>Breaker suggestions are informational. Always verify conductor ampacity, equipment ratings and your local electrical code before installing anything.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Convert watts to amps or amps to watts for DC, single-phase AC and three-phase AC circuits. Enter power, voltage and power factor to get current, apparent power and suggested breaker size.<\/p>\n","protected":false},"author":3168,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[4],"tags":[21],"class_list":["post-67321","post","type-post","status-publish","format-standard","hentry","category-engineering","tag-electrical"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/67321","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=67321"}],"version-history":[{"count":2,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/67321\/revisions"}],"predecessor-version":[{"id":67564,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/67321\/revisions\/67564"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=67321"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=67321"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=67321"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}