What Size Wire for 30 Amps at 50 Feet?

Answer
10 AWG copper

At 50 ft one way on a 240 V circuit, 10 AWG copper keeps voltage drop at 1.51%, under the recommended 3%. Ampacity alone would allow 10 AWG, but voltage drop decides the size at this distance. In aluminum, use 8 AWG.

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A
%
3% branch, 5% total (NEC note)
Phase
Conductor
Recommended wire
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How we calculated this

    For estimating and educational purposes only. Results are approximate and are not a substitute for a licensed professional, the manufacturer's instructions or your local code. Disclaimer

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    Voltage drop by wire size (30 A, 50 ft, 240 V)

    Copper wireDrop (V)Drop (%)Within 3%
    10 AWG3.63 V1.51%✓
    8 AWG2.29 V0.95%✓
    6 AWG1.47 V0.61%✓
    4 AWG0.92 V0.39%✓
    3 AWG0.73 V0.31%✓

    Voltage drop = 2 × 50 ft × 30 A × resistance ÷ 1000. Keeping it under 3% on branch circuits (5% total) is the NEC recommendation in the informational notes to 210.19 and 215.2.

    Frequently asked questions

    Is 10 AWG enough for 30 amps at 50 feet?

    It carries 30 A, but at 50 ft the voltage drop is 1.5%, which is acceptable.

    Does the distance include the return wire?

    No. Enter the one-way distance; the formula already counts both conductors.

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