Use this electronics calculation for a first-pass component, converter, signal, motor, or sensor estimate when the stated operating conditions and units match the device data.

Forward current (A)

Target continuous forward current of the LED.

Forward voltage (V)

Rated forward voltage of the LED at that current.

Supply voltage (V)

Supply voltage feeding the LED plus resistor.

Compute the series resistor that sets an LED operating point: R = (Vs - Vf) / I, dissipating the difference between supply and forward voltage. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Series resistor (Ω)

Required series resistance.

• LED forward voltage, current, power, efficacy, intensity, wavelength, and viewing angle depend on junction temperature, binning, drive waveform, optics, aging, and the manufacturer's measurement convention. Thermal design and absolute maximum ratings remain separate.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check the result against the current datasheet and worst-case operating corners, then verify the circuit or measurement with simulation and bench testing where failure matters.

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