Electrical & Electronics
LED Resistor Calculator
Calculate resistance, actual current and a safe power rating for single or series LED strings.
CALCULATOR
Enter values
Use a separate resistor for every parallel branch.
USAGE
How to use it
- Enter supply and LED forward voltages.
- Set LEDs per string, target current and parallel branch count.
- Check the E12/E24 recommendation and resistor dissipation.
FORMULA
Calculation
R = (Vs − n × Vf) / IExample
12 V, a 2 V LED and 20 mA requires 500 Ω; E24 suggests 510 Ω
TECHNICAL
Technical notes
- Use one series resistor per parallel branch.
- The recommended power rating includes headroom.