LED Resistor Calculator
Calculate the correct resistor value to safely limit current through an LED. Enter your supply voltage, LED forward voltage, and desired current.
V
V
mA
Calculated resistor
150.0 Ω
Nearest standard value
150 Ω
Power dissipation
60.0 mW
How to calculate the resistor for an LED
The formula is: R = (Vsupply - Vforward) / I, where R is the resistance in ohms, Vsupply is your power supply voltage, Vforward is the LED forward voltage drop, and I is the desired current in amperes.
Common LED forward voltages
| LED color | Typical forward voltage |
|---|---|
| Red | 1.8 – 2.2 V |
| Orange | 2.0 – 2.2 V |
| Yellow | 2.0 – 2.2 V |
| Green | 2.0 – 3.5 V |
| Blue | 3.0 – 3.5 V |
| White | 3.0 – 3.5 V |
Choosing a power rating
Select a resistor with a power rating at least twice the calculated power dissipation. Most standard through-hole resistors are rated at 250 mW (1/4 watt), which is sufficient for most LED circuits.