Wire ampacity chart

Pick the edition your AHJ enforces

Code adoption runs on its own schedule, state by state and sometimes city by city. Plenty of work in 2026 is still inspected against the 2020 or the 2023. The edition that matters is the one your authority having jurisdiction has adopted, not the newest one NFPA has published — which is why the edition is a control on this page rather than an assumption baked into it.

The article number moves too. What is Table 310.16 in the 2020 and later was Table 310.15(B)(16) in the 2017. The citation shown with each result follows the edition you pick, so it matches the book in the inspector's hand.

Ampacity is not the same as breaker size

The number this page gives you is the conductor's allowable ampacity. It is not automatically the overcurrent device rating. For 14, 12 and 10 AWG — and now 16 AWG copper and 14 AWG copper-clad aluminum in the 2026 — 240.4(D) caps the protection below the tabulated ampacity. That is why 12 AWG copper reads 25 A here and still lands on a 20 A breaker.

Which column, and why it is usually not 90 °C

Insulation rated 90 °C does not entitle you to the 90 °C column. Under 110.14(C) the circuit is limited by the lowest-rated component in it, and that is almost always the equipment terminations — commonly 60 °C at 100 A and below, 75 °C above. The 90 °C column earns its keep as the starting value for ambient temperature correction and conductor bundling adjustment, after which the corrected result still has to satisfy the termination limit.

Restricted rows are shown, never auto-selected

Some rows carry conditions written into the code itself. The 14 AWG aluminum row added in the 2026 applies to copper-clad aluminum only — using it for plain aluminum is a safety problem, not a technicality. The 16 AWG copper 75 and 90 °C values are for adjustment and correction rather than direct termination.

This page shows you those rows with the restriction stated, because hiding real data is its own kind of wrong. What it will not do is quietly select one for you in a sizing calculation — the conditions attached are ones only you can confirm on site. There is more on the 2026 changes in what actually changed in the NEC 2026.

Common questions

Why is 12 AWG copper rated 25 A but protected at 20 A?

Two separate rules are at work. Table 310.16 gives 25 A in the 75 °C column, which is the conductor's allowable ampacity. Then 240.4(D) caps overcurrent protection for small conductors — 20 A for 12 AWG copper — regardless of what the ampacity table says. The conductor can carry more than the breaker will let through, and that is by design.

Which temperature column should I use?

The one matching the lowest temperature rating in the circuit, which is usually the equipment terminations rather than the wire insulation. Under 110.14(C), terminations on equipment rated 100 A or less are commonly limited to 60 °C, and above that to 75 °C. THHN insulation rated 90 °C does not let you use the 90 °C column for sizing — that column is generally a starting point for derating and correction, not a value you terminate at.

Is 12 AWG aluminum really only 15 A?

Yes, in the 60 °C column, and this catches people constantly. Aluminum carries meaningfully less current than copper of the same size — 12 AWG aluminum is 15 A where copper is 20 A, and 10 AWG aluminum is 25 A where copper is 30 A. Reading across the wrong column of the table is one of the classic ways to undersize a conductor.

What changed in Table 310.16 in the NEC 2026?

The small-conductor rows at the top. 16 AWG copper gained all three columns rather than 90 °C alone, and a 14 AWG aluminum row appeared for the first time — restricted to copper-clad aluminum, not plain aluminum. The 18 AWG copper row moved into a note limited to specific wiring types. Everything from 8 AWG through 2000 kcmil is identical to the 2023.