LED Resistor Calculator
Find the correct current-limiting resistor for any LED circuit — single LEDs, series strings, and parallel arrays.
Single LED
R = (Vs − Vf) / If
V
V
Series String
R = (Vs − n×Vf) / If
V
#
V
Parallel Array
R = (Vs − Vf) / (n × If)
V
#
V
LED Quick Reference
| Colour | Typical Vf | Typical If | Wavelength | Notes |
|---|---|---|---|---|
| Red | 1.7–2.0 V | 10–30 mA | 620–750 nm | Most common; indicators |
| Orange | 1.9–2.2 V | 10–30 mA | 590–620 nm | Indicators, displays |
| Yellow | 2.0–2.2 V | 10–30 mA | 570–590 nm | Indicators |
| Green | 2.0–3.5 V | 10–30 mA | 495–570 nm | Wide variation by type |
| Blue | 2.5–3.5 V | 10–30 mA | 450–495 nm | Higher Vf than red/green |
| White | 3.0–3.5 V | 10–30 mA | — | Blue chip + phosphor |
| IR | 1.2–1.7 V | 20–100 mA | 780–1000 nm | Remote controls, sensors |
Tip: Never connect an LED directly to a voltage source without a resistor. The calculator rounds up to the next E24 standard value, so the LED never gets more current than you set, and sizes the resistor wattage at twice its dissipation. Max continuous current for most 5mm LEDs is 20–30 mA.