LED Series Resistor Calculator

Calculate the correct current-limiting resistor value and wattage for single or multiple LEDs in series.

LED Color Preset

Select an LED type to auto-fill typical values

Input Values

Enter your circuit parameters

Required Resistor
150 Ω
Exact: 150.00 Ω → Nearest E24: 150 Ω
R = (Vs − n×Vf) / If

Circuit Diagram

VsRLEDGNDI ↓

Circuit Details

Resistor Value (E24)150 Ω
Actual LED Current20.00 mA
Voltage Drop Across R3.00 V
Power in Resistor60.00 mW
Power per LED40.00 mW
Total Circuit Power100.00 mW
Min. Resistor Rating125mW (1/8W)

Quick Guide

Formula:

R = (Vs − n × Vf) / If
Vs
Supply Voltage
Vf
LED Forward Voltage
If
Forward Current
n
LEDs in Series

Typical Forward Voltages:

Red2V
Orange2.1V
Yellow2.1V
Green3.2V
Blue3.3V
White3.3V