LED Resistor Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the supply voltage, LED voltage and current.
- Press Calculate.
How it works
Resistor = (supply voltage − LED voltage) ÷ LED current. It drops the extra voltage so the LED gets the right current.
Worked example
12 V, 2 V LED, 20 mA. = 500 Ω.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.