LED Series Resistor Calculator
Find the right current-limiting resistor for any LED in seconds — includes E12 standard value and power dissipation.
Calculated resistor
150 Ω
Nearest E12 value
150 Ω
Power dissipation
60 mW
(60.0 mW)
Frequently Asked Questions
Why do LEDs need a series resistor?+
LEDs have a nearly constant forward voltage but no internal current limiting. Without a resistor, current rises uncontrollably and the LED burns out instantly.
What is a typical LED forward voltage?+
Red/yellow LEDs: ~2 V. Blue/green/white LEDs: ~3.0–3.5 V. Always check the datasheet for your specific LED.
What is the E12 value?+
E12 is a standard series of 12 preferred resistor values per decade (e.g. 10, 12, 15, 18…). The calculator shows the nearest E12 value you can actually buy.