Calculadoras

LED Resistor Calculator

Calculate the correct resistor value for any LED circuit — single LED, series, or parallel configurations with E24 standard values, power budget, and circuit diagrams

Parameters

Red: 1.8V – 2.2V (typical 2V)

Recommended Resistor
510 Ω
E24 standard value (exact: 500.0 Ω)
Voltage Drop
10.00 V
across resistor
Actual Current
19.6 mA
through each LED
Resistor Power
196 mW
use ≥ 1/4W rated
Efficiency
16.9%
LED power / total

Power Budget

LED Power40 mW
Resistor Loss196 mW
Total System Power236 mW

Circuit Diagram

+12V510 ΩGND→ I

LED Forward Voltage Reference

ColorTypical VfVf RangeTypical Current
Red2 V1.82.2 V20 mA
Orange2.1 V22.2 V20 mA
Yellow2.1 V22.2 V20 mA
Green2.2 V23.2 V20 mA
Blue3.2 V33.4 V20 mA
White3.2 V33.4 V20 mA
UV3.3 V3.23.6 V20 mA
Infrared1.5 V1.21.6 V20 mA

Formulas

Resistor Value
R = (V_supply − V_f) / I_led

Where V_f is LED forward voltage and I_led is desired current

Series LEDs
R = (V_supply − n × V_f) / I_led

All LEDs share the same current; voltages add up

Power Dissipation
P = (V_supply − V_f)² / R

Heat dissipated by the resistor — choose a rated wattage above this

Max Series LEDs
n_max = floor(V_supply / V_f)

Maximum LEDs possible in series (with no voltage headroom)

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