{"id":64422,"date":"2025-05-12T09:15:44","date_gmt":"2025-05-12T06:15:44","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=64422"},"modified":"2026-09-30T18:23:37","modified_gmt":"2026-09-30T15:23:37","slug":"led-series-resistor","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/engineering\/led-series-resistor\/","title":{"rendered":"LED Series Resistor 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\">Resistor Value for LED Current Limiting<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"64422\" data-favorite-title=\"LED Series Resistor\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/engineering\/led-series-resistor\/\" data-favorite-excerpt=\"Calculate the series resistor needed to safely drive an LED. Enter your supply voltage, the LED&#039;s forward voltage, and the desired current to get the resistor value in ohms.\" 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\/led-series-resistor\/\" method=\"POST\" class=\"calculator\" id=\"calculator-64422\" data-post=\"64422\"><fieldset class=\"fieldset-input is-1\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Supply voltage<\/label><div class=\"term\">Vs<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"supply_voltage\" id=\"field-1\" aria-describedby=\"calc-unit-1 calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"5\"\/><div class=\"unit\" id=\"calc-unit-1\">V<\/div><small id=\"calc-info-1\">Voltage from power supply<\/small><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-2\">LED forward voltage<\/label><div class=\"term\">Vf<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"led_forward_voltage\" id=\"field-2\" aria-describedby=\"calc-unit-2 calc-info-2\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0\" value=\"2\"\/><div class=\"unit\" id=\"calc-unit-2\">V<\/div><small id=\"calc-info-2\">Typical forward voltage of the LED<\/small><\/div><div class=\"field has-term\" id=\"input-3\"><label for=\"field-3\">LED 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=\"led_current\" id=\"field-3\" aria-describedby=\"calc-unit-3 calc-info-3\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0.001\" value=\"0.02\"\/><div class=\"unit\" id=\"calc-unit-3\">A<\/div><small id=\"calc-info-3\">Desired current through LED (e.g., 0.02 A = 20 mA)<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"64422\">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>Resistor Value<\/span><\/span><span class=\"field-value\" id=\"result-1\" 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><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=\"64422\" 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>LED Series Resistor 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\\[ R = \\frac{V_s - V_f}{I} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(R\\) \u2014 series resistor value (\u03a9)<\/li>\n<li>\\(V_s\\) \u2014 supply voltage (V)<\/li>\n<li>\\(V_f\\) \u2014 forward voltage of the LED (V)<\/li>\n<li>\\(I\\) \u2014 desired current through the LED (A)<\/li>\n<\/ul>\n<p>This is Ohm's law applied to the voltage the resistor must drop: the supply voltage minus the LED's forward voltage, divided by the current you want to flow through the circuit.<\/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>LED Series Resistor \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> you want to power a red LED with a forward voltage of 2 V from a 5 V supply at a current of 20 mA (0.02 A).<\/p>\n<p>\\[ R = \\frac{V_s - V_f}{I} = \\frac{5 - 2}{0.02} = \\frac{3}{0.02} = 150~\\Omega \\]<\/p>\n<p><strong>Result:<\/strong> a series resistor of 150 \u03a9 limits the current to 20 mA. The nearest standard value is 150 \u03a9 (E12 series); if unavailable, use 160 \u03a9 or 180 \u03a9 to be safe.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>Enter your <strong>Supply voltage<\/strong> in volts \u2014 for example, 5 for a USB power source or 3.3 for a microcontroller GPIO pin.<\/li>\n<li>Enter the <strong>LED forward voltage<\/strong> in volts. Check the LED datasheet; typical values are about 2 V for red, 3.2 V for blue and white.<\/li>\n<li>Enter the <strong>LED current<\/strong> in amperes. A common choice is 0.02 A (20 mA); for indicator LEDs, 0.005\u20130.01 A is often enough.<\/li>\n<li>Read the <strong>Resistor Value<\/strong> in ohms, then pick the nearest standard resistor value (rounding up is safer than rounding down).<\/li>\n<\/ol>\n<h2>What Is a Series Resistor for an LED?<\/h2>\n<p>An LED is a diode, not a resistor. Once the voltage across it exceeds its forward voltage, its current rises extremely steeply \u2014 a small increase in voltage causes a huge increase in current. Without anything to limit the current, an LED connected directly to a power supply will draw far more current than it can handle and burn out within seconds.<\/p>\n<p>A resistor placed in series with the LED solves this problem. It absorbs the excess voltage (the supply voltage minus the LED's forward voltage) and, by Ohm's law, sets the current to a safe, predictable value. This is the simplest and most common way to drive an LED, used everywhere from breadboard prototypes to production circuits.<\/p>\n<p>The calculator's result tells you the exact resistance for your target current. A higher resistance gives a dimmer LED and lower power dissipation; a lower resistance gives a brighter LED but risks exceeding its maximum current rating, typically 20\u201330 mA for standard 5 mm LEDs.<\/p>\n<p>If the calculator shows an error, check your inputs: the supply voltage must be greater than the LED's forward voltage, and the current must be positive. For example, a blue LED (\\(V_f \\approx 3.2\\) V) cannot be driven from a single 1.5 V battery without a boost converter.<\/p>\n<h2>Practical Tips and Limitations<\/h2>\n<ul>\n<li><strong>Round up to a standard value.<\/strong> Resistors come in standard series (E12, E24). For a calculated 143 \u03a9, use 150 \u03a9 rather than 120 \u03a9 \u2014 slightly less current is always safer.<\/li>\n<li><strong>Check the resistor's power rating.<\/strong> Power dissipated is \\(P = (V_s - V_f) \\times I\\). In the example above, \\(P = 3 \\times 0.02 = 0.06\\) W, well within a standard 0.25 W resistor. For high-current LEDs, use a resistor rated for the dissipation or a constant-current driver instead.<\/li>\n<li><strong>Forward voltage varies.<\/strong> The values in datasheets are typical; actual forward voltage changes with current, temperature, and manufacturing spread. Expect some variation in brightness between individual LEDs.<\/li>\n<li><strong>Multiple LEDs:<\/strong> LEDs in series share the same current, so subtract the sum of their forward voltages from the supply. LEDs in parallel each need their own series resistor \u2014 sharing one resistor causes uneven current distribution.<\/li>\n<li><strong>High-power LEDs<\/strong> (1 W and above) should not be driven with a simple resistor; use a dedicated constant-current driver for efficiency and safety.<\/li>\n<\/ul>\n<p>For current-limiting calculations with other components, see our <a href=\"https:\/\/wpcalc.com\/en\/engineering\/zener-diode\/\">Zener Diode Resistor Calculator<\/a>. If you end up combining resistors to reach the needed value, our <a href=\"https:\/\/wpcalc.com\/en\/engineering\/parallel-resistance\/\">Parallel Resistance Calculator<\/a> and <a href=\"https:\/\/wpcalc.com\/en\/engineering\/series-inductance\/\">Series Inductance Calculator<\/a> page's series formulas will help, and the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/wire-gauge\/\">Wire Gauge Calculator<\/a> is useful for sizing the wires that carry the current.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Calculate the series resistor needed to safely drive an LED. Enter your supply voltage, the LED's forward voltage, and the desired current to get the resistor value in ohms.<\/p>\n","protected":false},"author":70,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[4],"tags":[94],"class_list":["post-64422","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\/64422","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=64422"}],"version-history":[{"count":3,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/64422\/revisions"}],"predecessor-version":[{"id":65981,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/64422\/revisions\/65981"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=64422"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=64422"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=64422"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}