LED Resistor Calculator

Find the right resistor for your LED circuit

Single LED
Multiple LEDs
History
Information

Single LED Configuration

Circuit Diagram

Results

Required Resistor Value
-- Ω
Nearest Standard Resistor
-- Ω
Resistor Power (W)
-- W
Power Supply Current
-- mA

Multiple LEDs Configuration

Circuit Diagram

Results

Required Resistor Value
-- Ω
Nearest Standard Resistor
-- Ω
Resistor Power (W)
-- W
Power Supply Current
-- mA

Calculation History

LED Resistor Information

How to Calculate LED Resistors

The resistor value for an LED is calculated using Ohm's Law:

R = (Vs - Vf) / I

Where:

  • R = Resistor value (Ω)
  • Vs = Supply voltage (V)
  • Vf = LED forward voltage (V)
  • I = LED current (A)

Important Notes:

  • Standard resistors: E12/E24 series (10%, 5% tolerance)
  • Use a higher wattage resistor for safety (e.g., 0.25W or 0.5W)
  • For multiple LEDs, calculate resistors separately or use a series/parallel configuration
  • Check LED datasheet for exact forward voltage and current
  • Typical LED currents: 20mA for standard LEDs, 2-5mA for low-power indicators

Typical LED Voltages

  • Red LED: 1.8V - 2.2V
  • Green LED: 2.0V - 2.4V
  • Yellow LED: 2.0V - 2.4V
  • Blue LED: 3.0V - 3.6V
  • White LED: 3.0V - 3.6V

Series vs Parallel Connections

Series Connection: LEDs connected one after another. The supply voltage must be greater than the sum of all LED forward voltages.

Parallel Connection: LEDs connected side by side. Each LED needs its own current-limiting resistor for proper operation.