LED Series Resistor Calculator
Size a current-limiting resistor and see nearest standard values.
Ideal resistance
150 Ω
R = (Vs − Vf) / If
Resistor power
0.06 W
P = I²R
Nearest E12
150 Ω
Nearest E24
150 Ω
What is this tool?
An LED needs a series resistor so forward current stays near the datasheet target. R = (Vs − Vf) / If, and resistor dissipation is about I²R. This tool also suggests nearby E12/E24 preferred values.
How to use it
- Enter supply voltage, LED Vf, and desired forward current.
- Read calculated resistance, power, and nearest E-series suggestions.
- Pick a resistor wattage above the calculated dissipation with margin.
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