Electrical Tools
LED Resistor Calculator
Calculate the correct series resistor for LED circuits. Enter supply voltage, LED forward voltage, and current to get resistor value, power rating, and nearest E12 standard value.
Input
Result
Calculated Resistance
Nearest E12 Standard
Voltage across resistor
Power (calculated R)
Power (standard R)
⚠Supply voltage must be greater than LED voltage × count.
Fill in all fields to calculate.
R = (Vs − Vf × n) / If. Use rated power × 2 for safety margin.
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