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LED Series Resistor Calculator

These calculators give values for LED current limiting series resistors. The first calculator gives values based on standard LED types. This should only be used if the LED forward voltage and current are not known. The second calculator gives a more accurate value using these figures, which can be found in the suppliers catalogue. Preferred resistor values are also calculated; use the radio buttons on each calculator to select the preferred value series to use.

LED series resistor diagram

Calculate Resistor Value for Common LED Types:

Volts
E12 E24 E48 E96 E192 		Resistor = ?
Preferred Value = ?

Calculate Resistor Value from Vf and If:

Volts
Volts
Milliamps
E12 E24 E48 E96 E192 		Resistor = ?
Preferred Value = ?

Formula:

R = (Vs - Vf)  / If

= (Supply Voltage - Forward Voltage) / Forward Current

If is in units of Amps, NOT Milliamps! (20mA = 0.02A)

For more details see the technical data section here.

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