Physics

LED Resistor Calculator

Find the series resistor for an LED.

Calculated Output

Resistor value (Ω) 150

Resistor power (W) 0.06

Formula: R = (Vsupply − Vled) ÷ I

Step-by-Step Breakdown

1. Values used:

2. Supply voltage = 5 V

3. LED forward voltage = 2 V

4. LED current = 20 mA

6. Resistor value = 150Ω

7. Resistor power = 0.06W

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The math behind it

R = (supply voltage − LED forward voltage) ÷ LED current (in amps).

5 V, 2 V LED, 20 mA → 150 Ω.

Resistor wattage?

Choose a resistor rated above the power shown.