Power4all

LED Series Resistor Calculator

Advanced LED calculator with array designer, efficiency analysis, thermal calculations, and lifetime estimation.
Standard Resistors
Basic Calculator
Advanced Analysis
Array Designer

Basic LED Resistor Calculator

LED Series Resistor Formula:
R = (Vs - Vf × N) / If Presistor = (Vs - Vf × N) × If
5V Supply
9V Supply
12V Supply
20mA Current
V
Red
2.0V
Green
2.1V
Blue
3.6V
White
3.6V
Yellow
2.1V
Orange
2.2V
Amber
2.1V
IR
1.7V
V
Enter supply voltage, LED specifications, and current to calculate resistor value.

Efficiency Analysis

Enter values to see power efficiency calculations.

Circuit Diagram

Enter values to see the circuit diagram.

Auto-calculate as you type

LED Array Designer

Array Configuration:
Series: Total Vf = Vf × N, Same current Parallel: Same Vf, Total current = If × N

Array Configuration

Array Preview

Configure your LED array above to see the design.

Configure your LED array and click Design Array.

Advanced LED Analysis

LED Specifications

V
V
mA
°C
°C/W
hours

Thermal Analysis

Enter LED specifications to see thermal calculations.

Lifetime Estimation

Thermal analysis will provide lifetime estimates.

PWM Dimming Analysis

50%

Standard Resistor Finder

V
V
mA
Enter LED specifications to find suitable standard resistors.

LED Applications & Examples

Status Indicator LEDs

Application: Power and status indicators in electronic devices

  • Supply: 5V, LED: Red (2.0V), Current: 10mA
  • Resistor: 300Ω, Power: 30mW
  • Efficiency: 40% (LED power / Total power)

LED Strip Lighting

Application: Under-cabinet and accent lighting

  • Supply: 12V, LEDs: 3× White (3.6V), Current: 20mA
  • Resistor: 60Ω, Power: 120mW
  • Series configuration for even brightness

Automotive Applications

Application: Turn signals and brake lights

  • Supply: 12V, LED: Amber (2.1V), Current: 25mA
  • Resistor: 396Ω (use 390Ω), Power: 247mW
  • Use 0.5W resistor for safety margin