Led Resistor Calculator

Most common LEDís require a forward operating voltage from approximately
1.6 to 3.6 volts, which is the voltage used up by the LED (dropped) when current
is traveling in the appropriate direction (forward), this is the voltage that
must be applied across the leads of the LED from anode to cathode in order
for the LED to turn on, this rating varies according to LED colors. The suplied
voltage must be greater than the LED's forward voltage, it won't conduct until
youíve passed the appropriate forward voltage.

The resistor is used to limit the current passing through the LED and to
prevent it from burning. Note that no resistor is required if the voltage
source is equal to the voltage drop of the LED. Most of the common LEDs
have a maximum forward current of about 30mA but when used in stompboxes,
power consumption is a concern and usually a forward current from between
3 to 6 mA is good enough to make it bright as it should.

The calculator below based on the ohm's law can be used to determine the resistor
needed based on the desired current drawn and voltage source. Enter at least 2
values in the fields, select the voltage drop then click on the ’Calculate’ button.
 
Voltage Source (Vs) :
Volts (V)
Led Voltage Drop (VLed) :
Volts (V)
Current through the LED (ILed) :
Resistance (R) :
Closest Standard Resistor :
Power (P):
Watts (W)
    

ColorWavelength (nm)Brightness (mcd)Voltage Drop (VLed)
63012 - 30
1.8
5704 - 18
2.2
5904 - 18
2.1
470450 - 550
2.8
4002000 - 3000
3.4
6053000 - 4000
2.4
6252000 - 3000
3.1
Note : Typical values are shown in the chart above. It can be used
for quick reference, for more precise details see the datasheets.
Led Resistor Calculator

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