Math & Science
LED Resistor Calculator
Calculate resistor value for LED circuits
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Frequently asked questions
What voltage do LEDs need?
Varies by color: Red ~2V, Green ~2.2V, Blue/White ~3.2V
Series or parallel?
Series is simpler and ensures equal current. Parallel needs resistor per LED.
What resistor power rating?
Use at least 2x calculated power for safety margin.
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About this tool
This LED Resistor Calculator turns your inputs into practical results. Provide LED Current, Supply Voltage, and LED Forward Voltage to calculate E24 Series Value and Resistor Value.
Adjust values to compare scenarios and see how sensitive the result is. The calculation uses the numbers as entered, so double-check units and expect small differences from rounding in the displayed totals.