LED Resistor Calculator

ELECTRONICS

Calculate the correct resistor for any LED — voltage, current & power

R = (Vs − Vf) / If P = (Vs − Vf) × If

Supply voltage (Vs)

LED forward voltage (Vf)

Typical: Red/IR: 1.8–2.2V · Green/Blue/White: 3.0–3.6V

LED current (If)

Standard: 10–20mA for indicator LEDs, 20–30mA for high-brightness

                            Resistor value
                            —
                            Ω
                        

Nearest E12 standard — Ω

                            Resistor power
                            —
                            W
                        

Recommended rating — W

R = (Vs − Vf) / If | P = (Vs − Vf) × If

— Ω LED I = — mA

Current flows from Vs → R → LED → GND

Vf: 2.0 V Current: 20 mA Brightness: ●

Find the nearest standard value for your calculated resistor

Calculated resistance

Series

tolerance

                            Nearest standard
                            —
                            Ω
                        

Difference — %

Actual current — mA

E-series: E12, E24, E48, E96

Common values in the selected E-series

Calculate resistor for a string of LEDs connected in series

Supply voltage (Vs)

LED forward voltage (Vf)

Number of LEDs

LEDs

LED current (If)

                            Total LED voltage
                            —
                            V
                        

                            Resistor value
                            —
                            Ω
                        

Resistor power — W

Voltage margin — V

V_led_total = Vf × N | R = (Vs − V_led_total) / If

3 LEDs R = — Ω

Series LEDs share the same current