LED Resistor Calculator
Find the current-limiting resistor value for an LED, based on your supply voltage and target current.
Exact resistance needed
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Nearest standard resistor
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Power dissipated by resistor
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The Formula Behind This Calculator
The resistor value is calculated as R = (Vsupply − n × Vfwd) ÷ I, where Vfwd is the LED's forward voltage, n is the number of LEDs wired in series, and I is your target current. We round up to the nearest standard E12 resistor value so the actual current never exceeds your target.
Want the full background on this formula? Read Ohm's Law Explained or What Is a Resistor?. You can also use the Resistor Color Code Calculator to find the color bands for your result.