💡 LED Series Resistor Calculator for Electrical
Estimate a current-limiting resistor for a simple LED circuit.
This free tool helps you turn project measurements into a practical planning estimate. Enter values in Vaelden’s interactive calculator, review the result, and confirm important assumptions against supplier data, measurements, codes or qualified advice before committing materials or money.
Open the LED Series Resistor calculator →
How to calculate led series resistor
Method: Series resistance = (supply voltage − LED forward voltage) ÷ LED current
- Use worst-case supply voltage.
- Use forward voltage from the LED datasheet at the intended current.
- Choose the next suitable standard resistance and verify resistor power.
Worked example
Using these planning inputs:
- Supply voltage: 5 V
- LED forward voltage: 2 V
- Target LED current: 15 mA
Minimum series resistance: 200.0 Ω
Reality check: Multiple LEDs, pulsed drive, temperature and parallel strings need a proper driver design rather than one shared resistor.
Before you calculate
Use consistent units and the best measured inputs available. Real materials, equipment, site conditions and tolerances can change the result. Vaelden shows planning estimates; regulated, structural, electrical, plumbing, pressure and other safety-critical work still requires appropriate local compliance and professional advice.