LED Current-Limiting Resistor Calculator
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Definitions
Formulae
Instructions
Introduction:
The calculator on this page 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.
Definitions:
- Vt
- Total Voltage drop across the LED and resistor
- VLED
- Voltage drop rating, across the LED or LEDs in series
- I
- Current rating of the LED / current through the finished system
- R
- Value of Resistor required to limit the current
Instructions
- Enter a value into each text-box in the form below.
- Choose appropriate unit-sizes for each value from each drop-down list.
- Hit the ENTER or RETURN key on your keyboard, or press the 'CalcResult' button below the input fields.
- A results area will appear at the bottom of the page, showing the required resistance value.
- 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.
See Also: