LED resistor calculator

Series resistor for LEDs — R=(Vs−n·Vf)/I, nearest E24 value, power and wattage suggestion.

Computed in this browser. Nothing is sent anywhere.

Rounds up to the nearest E24 value (safer current) and suggests a wattage rating ≥ 2× dissipation. Check your LED's datasheet for the real forward voltage — it varies by color and bin.

How to use

  1. Enter supply voltage, LED forward voltage, and target current.
  2. Set the series LED count.
  3. Read the ideal and E24 resistance plus wattage.

What it supports

Rounds up to the nearest E24 value (safer current) and suggests a rating ≥ 2× the dissipation. Supply must exceed the total forward drop — the tool says so when it does not. Check the LED's datasheet for real Vf.

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