LED Resistor Calculator

Required Resistor: -
Closest Standard: -
Power Dissipation: -
LED Resistor Calculator

LED Resistor Calculator

How to Calculate LED Resistor

To calculate the appropriate resistor for an LED, we use Ohm's Law:

R = (Vsource - VLED) / ILED

Where:

  • R: Required resistor value in ohms (Ω).
  • Vsource: Voltage of the power supply in volts (V).
  • VLED: Voltage required to operate the LED in volts (V).
  • ILED: LED current in amperes (A).

Voltage and Current Values for 5mm LEDs

5mm LEDs have different voltage and current values depending on their color:

  • Red LED: 1.8V - 2.2V, 20mA (0.02A).
  • Yellow LED: 2.0V - 2.2V, 20mA (0.02A).
  • Green LED: 2.0V - 3.2V, 20mA (0.02A).
  • Blue LED: 3.0V - 3.5V, 20mA (0.02A).
  • White LED: 3.0V - 3.5V, 20mA (0.02A).

Example Calculation

If you have a 9V power supply and use a red LED that requires 2V to operate and consumes 20mA (0.02A) of current, the resistor is calculated as follows:

R = (9V - 2V) / 0.02A = 7V / 0.02A = 350Ω

Conclusion

Using this method, you can determine the correct resistor to protect the LED and prevent excessive current from damaging it.