LED Resistor Calculator

Pick the right resistor to drive an LED safely.

Supply voltage (V)

LED color

LED current If (mA)

LEDs in series

Resistor needed

160.0 Ω

calculated value

Nearest E12 (next higher)

180.0 Ω

Power dissipated

64.0 mW

Voltage drop on resistor

3.20 V

Recommended rating

1/4 W

R = (Vs - n × Vf) / If, with current in amps. The recommended rating gives you at least 2x headroom over the actual dissipation, which is the standard rule of thumb. E12 is the 12-step preferred resistor series used for most through-hole parts.

About

Enter your supply voltage, LED forward voltage, and target current. Get the resistor value and standard nearest E12 size. Plus the power dissipated by the resistor (so you can pick a 1/4W or 1/2W).

How to use

Enter supply voltage.
Enter LED forward voltage and current.
See the recommended resistor and power rating.

FAQ

What's the LED forward voltage?+

Red is 1.8-2.0V. Yellow/Green: 2.0-2.2V. White/Blue: 3.0-3.4V. Check the LED datasheet for exact values.

What current is safe?+

Most indicator LEDs are rated for 20mA. Run them at 15mA for longer life. High-brightness LEDs can take more, but check the datasheet.