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LED Resistor Calculator — E12/E24 Value, Color Code & Power

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Supply voltage (V) LED forward voltage, each (V) Prefer the datasheet value at the intended current.LEDs in series Target LED current (mA) Use the LED datasheet current range.Driver / switch voltage drop (V) Preferred resistor series Power headroom (%) 100% means target at least 2× the calculated resistor dissipation.

Calculated result

200 Ω E24 resistor

Ideal resistance: 200 Ω · resistor drop 3 V

4-band color code: red · black · brown · gold (±5%)

Estimated current at 200 Ω: 15 mA (target 15 mA)

Resistor dissipation at selected value: 0.045 W

Power with 100% entered headroom: 0.09 W · next listed rating ≥ 0.125 W

LED-string electrical power at selected current: 0.03 W

Show the working

1. Voltage left for resistor = 5 − (1 × 2) − 0 = 3 V.
2. Ideal R = 3 ÷ 0.015 = 200 Ω.
3. Round upward to E24 → 200 Ω; I = 3 ÷ 200 = 15 mA.
4. Selected nominal resistor color code → red · black · brown · gold (±5%).
5. PR = VRI = 3 × 0.015 = 0.045 W.

Simple DC low-current LED string model. Verify LED Vf/current limits, resistor tolerance and thermal derating; high-power LEDs generally require an appropriate current driver.

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