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)
Power Budget
Circuit Diagram
LED Forward Voltage Reference
| Color | Typical Vf | Vf Range | Typical Current |
|---|---|---|---|
| Red | 2 V | 1.8 – 2.2 V | 20 mA |
| Orange | 2.1 V | 2 – 2.2 V | 20 mA |
| Yellow | 2.1 V | 2 – 2.2 V | 20 mA |
| Green | 2.2 V | 2 – 3.2 V | 20 mA |
| Blue | 3.2 V | 3 – 3.4 V | 20 mA |
| White | 3.2 V | 3 – 3.4 V | 20 mA |
| UV | 3.3 V | 3.2 – 3.6 V | 20 mA |
| Infrared | 1.5 V | 1.2 – 1.6 V | 20 mA |
Formulas
R = (V_supply − V_f) / I_ledWhere V_f is LED forward voltage and I_led is desired current
R = (V_supply − n × V_f) / I_ledAll LEDs share the same current; voltages add up
P = (V_supply − V_f)² / RHeat dissipated by the resistor — choose a rated wattage above this
n_max = floor(V_supply / V_f)Maximum LEDs possible in series (with no voltage headroom)
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