Which resistor for an LED?
Compute an LED series resistor from supply voltage, forward voltage and target current, rounded to the next standard E12 value.
V
V
mA
- Exact resistor
- 200 Ω
- Standard value (E12)
- 220 Ω
- Actual current
- 13.64 mA
- Resistor power
- 40.91 mW
Formula
R = (Vsupply − Vf) / I
A red LED drops about 2 V, a blue or white one about 3 V. On a 5 V Arduino pin, aim for 10–15 mA: 220 Ω is the classic value.
Check your result in a real circuit
Wire the circuit in the Circuitly simulator and measure voltage and current with the multimeter — free, no account.
Open the simulator