Resistors & LEDs

LED Resistor Calculator

LED Resistor Calculator. Resistor color codes and LED series-resistor calculations. Calculations run in your browser. Entered electrical values are not uploaded to our server.

Inputs

Supply voltage

LED forward voltage

LEDs in series

Target LED current

Calculations run in your browser. Entered electrical values are not uploaded to our server.

ⓘMathematical estimate only. Verify equipment datasheets, manufacturer instructions, electrical codes and qualified design before real-world use.

Formula & method

R = (Vsupply − Vf × count) / I; Presistor = I²R

Worked example

12 V supply, 2 V LED, 20 mA → 500 Ω

Assumptions & safety boundary

Mathematical estimate only. Verify equipment datasheets, manufacturer instructions, electrical codes and qualified design before real-world use.