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Resistor for a blue LED on 12 volts
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470 Ω
resistor for a blue LED on 12 V at 20 mA (calculated 440 Ω)
Blue LED on 12 V by current
| LED current | Exact resistor | Standard value |
|---|---|---|
| 5 mA | 1,760 Ω | 1,800 Ω |
| 10 mA | 880 Ω | 910 Ω |
| 15 mA | 587 Ω | 620 Ω |
| 20 mA | 440 Ω | 470 Ω |
Assumes 3.2 V forward voltage; check your LED datasheet. One LED per resistor; for several LEDs in series subtract each forward voltage from the supply.
Other LED colors on 12 V
FAQ
What resistor for a blue LED on 12V?
For a blue LED (about 3.2 V forward voltage) at 20 mA on 12 V: R = (12 − 3.2) ÷ 0.020 = 440 Ω. The next standard value is 470 Ω, which gives 18.7 mA.
What resistor is safe for an Arduino or breadboard with a blue LED on 12V?
A 910 Ω resistor limits the current to about 10 mA - dimmer but safe and long-lived. Use 470 Ω for full brightness.
What power rating does the resistor need?
At 18.7 mA it dissipates about 165 mW, so a 1/2 W resistor is enough.
LED resistor calculator · all supply voltages · Ohm’s law
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