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  3. LED series resistor calculator
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LED series resistor calculator

Picks the series resistor for one LED or a string: exact value, nearest preferred value, actual current, and power per resistor.

This tool is in beta

Still being tested. If a result looks wrong, tell us.

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Enter the LED and the supply to size the resistor.

This is a plain series resistor for an indicator or a low-power string. It assumes one resistor in series with the whole string, so every LED carries the same current. It does not model LED binning, thermal runaway, or constant-current drivers, and a parallel string needs one resistor per leg. The suggested rating doubles the calculated dissipation because running a resistor near its rating cooks it and drifts its value.

The LED and the supply

V
V
mA
Preferred value seriesThe nearest part is rounded up, so real current lands at or under your target
More settings▾
Optional. Leave blank to size with the nearest preferred value.
ohms

Voltages sit within ±1,000 V, current within 10,000 mA, the string between 1 and 200 LEDs, a fitted resistor up to 100,000,000 ohms.

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