Wire Size Chart: AWG Ampacity for Copper and Aluminum

Answer
14 AWG = 15 A · 12 AWG = 20 A · 10 AWG = 30 A

Use the 75 °C column for THHN/THWN in conduit and most breaker terminals, and the 60 °C column for NM-B (Romex) house cable. Small conductors are capped at 15, 20 and 30 A by NEC 240.4(D).

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AWG ampacity chart (NEC 310.16, 30 °C ambient)

Wire sizemm²Copper 60 °C (NM-B)Copper 75 °C (THHN)Aluminum 75 °C
14 AWG2.0815 A15 A–
12 AWG3.3120 A20 A15 A
10 AWG5.2630 A30 A25 A
8 AWG8.3740 A50 A40 A
6 AWG13.355 A65 A50 A
4 AWG21.270 A85 A65 A
3 AWG26.785 A100 A75 A
2 AWG33.695 A115 A90 A
1 AWG42.4110 A130 A100 A
1/0 AWG53.5–150 A120 A
2/0 AWG67.4–175 A135 A
3/0 AWG85.0–200 A155 A
4/0 AWG107.0–230 A180 A
250 kcmil127.0–255 A205 A
300 kcmil152.0–285 A230 A
350 kcmil177.0–310 A250 A
400 kcmil203.0–335 A270 A
500 kcmil253.0–380 A310 A

No more than three current-carrying conductors in a raceway or cable. For more conductors or hot locations, apply NEC adjustment factors. Long runs need a larger size for voltage drop: use the calculator below.

A
%
3% branch, 5% total (NEC note)
Phase
Conductor
Recommended wire
–
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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    How to read the chart

    Find the load current, then pick the first size whose ampacity is equal to or greater than the breaker rating. For continuous loads (3 hours or more, like EV chargers and water heaters) size the breaker and wire for 125% of the load.

    Why aluminum is one or two sizes larger

    Aluminum conducts about 61% as well as copper, so the same ampacity needs a larger cross-section. That is why a 100 A feeder is 3 AWG copper but 1 AWG aluminum.

    Wire Size Chart: AWG Ampacity for Copper and Aluminum
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    Frequently asked questions

    What size wire for 20 amps?

    12 AWG copper. 14 AWG is limited to 15 A.

    What size wire for 30 amps?

    10 AWG copper, or 8 AWG aluminum.

    What size wire for 50 amps?

    6 AWG copper NM-B or 8 AWG copper THHN in conduit (75 °C terminals), or 6 AWG aluminum.

    What size wire for 100 amps?

    3 AWG copper or 1 AWG aluminum at 75 °C. Dwelling services may use NEC 310.12: 4 AWG copper or 2 AWG aluminum.

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