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Resistor for a red LED on 3.3 volts
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68 Ω
resistor for a red LED on 3.3 V at 20 mA (calculated 65 Ω)
Red LED on 3.3 V by current
| LED current | Exact resistor | Standard value |
|---|---|---|
| 5 mA | 260 Ω | 270 Ω |
| 10 mA | 130 Ω | 130 Ω |
| 15 mA | 87 Ω | 91 Ω |
| 20 mA | 65 Ω | 68 Ω |
Assumes 2.0 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 3.3 V
FAQ
What resistor for a red LED on 3.3V?
For a red LED (about 2.0 V forward voltage) at 20 mA on 3.3 V: R = (3.3 − 2.0) ÷ 0.020 = 65 Ω. The next standard value is 68 Ω, which gives 19.1 mA.
What resistor is safe for an Arduino or breadboard with a red LED on 3.3V?
A 130 Ω resistor limits the current to about 10 mA - dimmer but safe and long-lived. Use 68 Ω for full brightness.
What power rating does the resistor need?
At 19.1 mA it dissipates about 25 mW, so a 1/4 W resistor is enough.
LED resistor calculator · all supply voltages · Ohm’s law
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