LED Resistor Calculator

Enter supply voltage, LED forward voltage, desired current, and LED count to estimate a safe series resistor value.

Supply voltage (V)

LED forward voltage (V)

LED current (mA)

LEDs in series

—Ideal series resistance

—Nearest E12 value

—Resistor dissipation

—Resistor voltage drop

—Total LED Vf

LED forward voltage varies by device, current, and temperature. Use the LED manufacturer’s datasheet and stay within component ratings. Intended for low-voltage electronics only.

How to use this LED Resistor Calculator

Calculate a series resistor and resistor power for one or more LEDs in series. Enter your values above and the result is calculated directly in your browser. No account is required.

Fast answer, clear inputs

This tool is built around one job: give the answer quickly without forcing a signup or hiding the result. Related tools are linked nearby when the next calculation or conversion is useful.