TheCircuitDogCircuit Fundamentals
LED Resistor Calculator
Size a series resistor for one or more LEDs in a string. The calculator estimates the resistor value and power dissipation.
Enter the values above and select Calculate result.
Formula
R = (Vsupply − N × Vf) / I
Worked example
With 5 V supply, one 2 V LED and 10 mA target current: R = (5 − 2) / 0.01 = 300 Ω and resistor loss ≈ 0.03 W.
Engineering notes
Choose a nearby higher standard value if uncertain, check LED absolute maximums and use a resistor with adequate power derating.
Always compare calculated values with the actual component datasheet, tolerance stack-up, operating temperature and circuit conditions before applying them to hardware.