LED Resistor Calculator

Calculate current-limiting resistor value and power rating for LED circuits.

Source voltage.
V
LED forward voltage drop (red≈2V, white≈3.2V).
V
Desired LED current.
mA
Number of LEDs in series string.

Results

Resistor Value-Ω
Resistor Power-mW
Total LED Power-mW
LED Efficiency-%
References: Typical LED Datasheets; Horowitz & Hill Art of Electronics