Calculate the resistor a LED needs from its color, supply and current, with the nearest standard value, actual current and resistor power.
A LED does not limit its own current and fails without a series resistor. The resistor is R = (Supply − LED voltage) / Current. The calculator uses the typical forward voltage for the color, rounds up to the next standard value and also shows the current at the LED’s maximum forward voltage.
R = (5 V − 1.85 V) / 15 mA = 210 Ω. If the LED voltage is at its maximum, the current is 11.4 mA. 10–15 mA is enough for an Arduino pin.
| Color | Vf typ / max | Max current |
|---|---|---|
| Red | 1.85 / 2.5 V | 30 mA |
| Orange | 1.95 / 2.3 V | 25 mA |
| Yellow | 1.95 / 2.4 V | 30 mA |
| Green (classic) | 2.2 / 2.5 V | 25 mA |
| Green (pure) | 3.2 / 4 V | 30 mA |
| Blue | 3.3 / 4 V | 30 mA |
| White | 3.3 / 4 V | 30 mA |
| UV 395 nm | 3.2 / — V | 30 mA |
| IR 940 nm | 1.2 / 1.6 V | 50 mA |
Typical values from Kingbright datasheets. Green comes in two kinds: older yellowish (GaP) about 2.2 V, pure green (InGaN) about 3.2 V. The package (3 mm, 5 mm, SMD) doesn't change the voltage.
