ConverterHub

LED Resistor Calculator

Size the series resistor for your LED in seconds

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

This calculator sizes the series resistor an LED needs using R = (Vsupply − Vf) / I — supply voltage minus the LED's forward voltage, divided by the target current — then shows the power the resistor dissipates and the nearest standard E12 resistor value you can actually buy.

Electronics hobbyists, Arduino and Raspberry Pi builders, and students use it every time they wire an LED to a circuit, since running an LED without the right resistor either burns it out (too little resistance) or leaves it dim (too much).

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