When using standard non-addressable LEDs, for example when using the Inner Light expansion board (which has 6 x 5V DC outputs), it is usually necessary to include a resistor to limit the current passing through the LED to prevent damage. This calculator lets you work out the value of any resistor you may require, given the parameters of the LED you are using, and the power supply. Typical values are shown below. You can also enter the color coding bands of any resistor you may have, to identify its value.

LED Parameters

Supply / Output DC Voltage (Volts V):
LED Forward Voltage (Volts V) - see typical examples
LED Current (milliamps mA) - see typical examples

Calculate resistor value in ohms
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Resistor Color Coding Bands

(click to alter and see the resulting resistor value)

Typical Values:

LED Color	LED Voltage Range (V)	LED Current (mA)
Red	1.8 - 2.2	10 - 20
Amber	2.0 - 2.4	10 - 20
Yellow	2.0 - 2.4	10 - 20
Green	2.0 - 3.2	10 - 20
Blue	3.0 - 3.7	10 - 20
White	3.0 - 3.5	10 - 20