LED Dropping Resistor Calculator

All LEDs require current limiting, without a current limiting mechanism, LEDs will usually burn out in under a second. Adding a simple resistor is one of the easiest ways to limit the current.

The two online calculators below allow for the automatic calculation of the necessary current limiting resistor and power rating for either running a single LED from a power source or running multiple LEDs in series from a power source.

If you require assistance in determining the color code for a resistor value specified, please be sure to visit our Resistor Color Code Calculation Page.

When using LEDs in automotive applications, the actual voltage in a vehicle is not 12 volts, rather they operate between 13.8 to 14.5 volts.

If you are looking for a quick reference chart, we have prepared one that lists various LEDs and power supply voltages along with the necessary resistor value to properly limit the current to the LED.

Note: If you are using the LED in a battery powered circuit that will be charged while the LED is connected, be sure to use the highest expected charging voltage, and not the battery voltage!

 

 

Battery or Supply Voltage:  Volts
Voltage Drop Across LED:  Volts
Desired LED Current:  Milliamps
   
 
Calculated Limiting Resistor:  Ohms
Nearest standard resistor value:  Ohms
Calculated Resistor Wattage:  Watts
Safe power rating of:  Watts
  

 

Battery or Supply Voltage:  Volts
Voltage Drop Across LED:  Volts
Desired LED Current:  Milliamps
LEDs To Connect In Series:
 
Calculated Limiting Resistor:  Ohms
Nearest standard resistor value:  Ohms
Calculated Resistor Wattage:  Watts
Safe power rating of:  Watts