TradeCalcs

Wire Ampacity Chart (NEC Table 310.16) — Copper, 60/75/90°C

One table sits under every wire-size decision in American branch-circuit work: NEC Table 310.16. This page prints the copper columns with the small-conductor caps applied, plus the circular-mil areas that voltage-drop math needs.

Quick answer: NEC Table 310.16 copper: 14 AWG = 15/20/25 A (60/75/90°C), 12 AWG = 20/25/30, 10 AWG = 30/35/40, 8 AWG = 40/50/55, 6 AWG = 55/65/75, 4 AWG = 70/85/95, 2 AWG = 95/115/130, 1/0 = 125/150/165, 4/0 = 195/230/260. But 240.4(D) caps small conductors: 14→15 A, 12→20 A, 10→30 A for everyday circuits.

The table (copper, dry locations)

  • 14 AWG — 15 / 20 / 25 A — cap 15 A — 4,110 cmil
  • 12 AWG — 20 / 25 / 30 A — cap 20 A — 6,530 cmil
  • 10 AWG — 30 / 35 / 40 A — cap 30 A — 10,380 cmil
  • 8 AWG — 40 / 50 / 55 A — 16,510 cmil
  • 6 AWG — 55 / 65 / 75 A — 26,240 cmil
  • 4 AWG — 70 / 85 / 95 A — 41,740 cmil
  • 3 AWG — 85 / 100 / 115 A — 52,620 cmil
  • 2 AWG — 95 / 115 / 130 A — 66,360 cmil
  • 1 AWG — 110 / 130 / 145 A — 83,690 cmil
  • 1/0 — 125 / 150 / 165 A — 105,600 cmil
  • 2/0 — 145 / 175 / 195 A — 133,100 cmil
  • 3/0 — 165 / 200 / 225 A — 167,800 cmil
  • 4/0 — 195 / 230 / 260 A — 211,600 cmil
  • 250 kcmil — 215 / 255 / 290 A — 250,000 cmil

Which column do I use?

The lowest rating in the chain: conductor insulation, termination rating, and device rating. Modern breakers and equipment terminations are typically 75°C, so the 75°C column is the working default. The 90°C column exists mostly as a derating starting point — you may start at 90°C values when applying ambient/bundle correction factors, but you must land at or below the 75°C termination value.

The 240.4(D) override

For branch circuits up to household sizes, the small-conductor rule caps protection regardless of the table: 14 AWG at 15 A, 12 AWG at 20 A, 10 AWG at 30 A. That's why 12 AWG 'rated 25 A' at 75°C still can't feed a 25 A breaker in a normal circuit. Exceptions exist (motor circuits, some 90°C-use cases with specific conditions), but the caps are the everyday rule.

What the table doesn't include

  • Voltage drop — a 15 A, 200 ft circuit passes this table and fails the 3% target badly.
  • Derating — ambient heat above 30°C and bundling (>3 CCC in a raceway) multiply downward.
  • Aluminum — separate columns (roughly two trade sizes lower ampacity).
  • Adjustment for continuous loads — sizing at 125% happens before this table.

Frequently Asked Questions

What is ampacity?
The maximum current a conductor can carry continuously without exceeding its insulation temperature rating. It depends on material, size, insulation rating, and installation conditions — which is why the table has three temperature columns and correction factors exist.
Why does 75°C matter so much?
Because it's the standard termination temperature of modern breaker lugs and equipment. The conductor may be 90°C cable, but where it lands on a lug, 75°C rules. Mismatched (older 60°C) terminations drag the whole circuit down to 60°C values.
Is this table valid for NM cable (Romex)?
NM uses the 60°C column (its insulation is rated 90°C but the code requires 60°C ampacity per 334.80), with the 240.4(D) caps. THHN/THWN in conduit works from the 75/90°C columns as installed.
Where's aluminum?
Aluminum ampacity runs about two trade sizes below copper (6 AWG Al ≈ 4 AWG Cu territory). Service entrances use it economically at larger sizes. The full aluminum columns live in Table 310.16 itself; this page focuses on the copper numbers branch work uses daily.
How does derating work with this table?
Start from the 90°C column (if the cable is 90°C-rated), multiply by ambient-temperature and bundling correction factors, then compare to the 75°C termination limit — the derated value must clear your load AND the termination cap. The wire size calculator applies the basic table; complex derates stack manually.

More tools used in this guide

Wire Size Calculator
Enter load current and terminal temperature rating — get the minimum AWG by ampacity, with the 240.4(D) small-conductor caps already applied.
Voltage Drop Calculator
Enter voltage, load amps and run length — get the voltage drop in volts and percent for every wire size, with the smallest size that holds 3%.
Conduit Fill Calculator
Pick conduit type and trade size, list your wires — get the fill percentage against the NEC 40% limit and the max count of that wire.

More guides

What Is Voltage Drop?
What voltage drop is, why it matters, the 3%/5% targets, and how to fix a run that fails.
How to Size a Breaker
The five-step branch-circuit sizing method — load, 125% rule, standard sizes, wire pairing, and the mistakes inspectors catch.