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.

Calculate Resistor Value for Common LED Types:

Enter Supply Voltage:        Volts		Resistor = ? Preferred Value = ?
Choose LED Type:        Standard Low Current High Brightness Super Bright Ultra Bright Standard Blue
Select preferred series (optional): E12    E24    E48    E96    E192

Calculate Resistor Value from Vf and If:

Enter Supply Voltage:        Volts		Resistor = ? Preferred Value = ?
Enter LED Forward Voltage, Vf:        Volts
Enter LED Forward Current, If:        Milliamps
Select preferred series (optional): E12    E24    E48    E96    E192

Formula:

R = (V_s - V_f)  / I_f

= (Supply Voltage - Forward Voltage) / Forward Current

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

For more details see the technical data section here.

Page last modified: 06 March 2009
Copyright © Simon Carter 1999-2009
Disclaimer & Copyright info.