LED Current-Limiting Resistor Calculator

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Introduction:

LEDs are simple components, but getting the fundamentals right matters. This calculator provides a straightforward starting point for designing reliable LED circuits, helping bridge the gap between basic theory and practical electronics.
Building an LED circuit? Use this calculator to find the resistor value you need in seconds.
This calculator guides you on how to detemine the correct size/value/resistance of current-limiting resistor required to run an LED at the right current for that type.
(The datasheet for your chosen LED will specify a max-current, but you should always design your circuit for a slightly lower current for safety, and to prevent premature burn-out of the component.)
This calculator will also work for two or more LED's in series, if you first add up the voltage drop required for each LED.
Click on any of the links at the top of the page to reveal (or hide) more information about this calculator.

Instructions

  1. Enter a value into each text-box in the form below.
  2. Choose appropriate unit-sizes for each value from each drop-down list.
  3. Hit the ENTER or RETURN key on your keyboard, or press the 'CalcResult' button below the input fields.
  4. A results area will appear at the bottom of the page, showing the required resistance value.
  5. Press the 'Clear Results' button if you wish to discard the current results list, otherwise further calculations will be added to the bottom of the current results list.

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