LED Series Resistor Calculation
Calculate the series resistor needed for an LED.
V
V
mA
Result
150 Ω
Required resistance: 150 Ω
Result in all units
Step-by-step solution
R = (Vs − Vled) / I
What Is an LED Resistor?
An LED resistor is the protective resistor that must be connected in series to run an LED safely. It prevents the LED from being damaged.
How is it calculated?
How Is It Calculated?
R = (V_source − V_led) ÷ I_led
- Enter the supply voltage, the LED forward voltage and its current.
- Divide the voltage difference by the LED current.
Frequently Asked Questions
What is the usual LED current?
For standard LEDs the typical current is in the 10–20 mA range; rely on the manufacturer's value.