Wire Ampacity ChartWire Ampacity Chart

NEC 2023 · Table 310.16 · 240.4(D) · 250.122 · 250.66

Wire gauge ampacity, 14 AWG to 4/0

Every wire gauge from 14 AWG through 4/0, with its ampacity in the 60°C, 75°C, and 90°C columns of NEC Table 310.16, the breaker that 240.4 permits on it, the ground it takes, and how far it reaches at 3% voltage drop.

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Ampacity by wire gauge

Ampacity by conductor size from NEC Table 310.16, at 30°C ambient with three or fewer current-carrying conductors.
SizeCopperAluminum
60°C75°C90°C60°C75°C90°C
14 AWG15 A20 A25 A———
12 AWG20 A25 A30 A15 A20 A25 A
10 AWG30 A35 A40 A25 A30 A35 A
8 AWG40 A50 A55 A35 A40 A45 A
6 AWG55 A65 A75 A40 A50 A55 A
4 AWG70 A85 A95 A55 A65 A75 A
3 AWG85 A100 A115 A65 A75 A85 A
2 AWG95 A115 A130 A75 A90 A100 A
1 AWG110 A130 A145 A85 A100 A115 A
1/0 AWG125 A150 A170 A100 A120 A135 A
2/0 AWG145 A175 A195 A115 A135 A150 A
3/0 AWG165 A200 A225 A130 A155 A175 A
4/0 AWG195 A230 A260 A150 A180 A205 A

Ampacities are NEC Table 310.16 values at 30°C ambient with three or fewer current-carrying conductors. A dash means the table leaves that cell blank, which happens for aluminum at 14 AWG and for no other size in this range.

Rules behind the table

  • NEC 240.4(D) caps overcurrent protection at 15 A for 14 AWG copper, 20 A for 12 AWG copper, 30 A for 10 AWG copper, 15 A for 12 AWG aluminum, and 25 A for 10 AWG aluminum. Those five caps equal the 60°C ampacities, so a higher column can never buy a smaller conductor on those sizes and can never buy a larger breaker either.
  • Every other size is protected from 240.4(B), which allows the next standard rating above the ampacity when the ampacity falls between two ratings in 240.6(A). That is how a 6 AWG copper conductor with 55 A of ampacity sits on a 60 A device.
  • Which column applies is settled by 110.14(C): 60°C for equipment rated 100 A or less, 75°C above that, unless the equipment is listed and marked for a higher temperature.
  • 334.80 and 340.80 override both for cable: NM-B and UF-B are read from the 60°C column whatever the terminals are marked.

Reading one size

Take 12 AWG copper. Table 310.16 gives it 20 A at 60°C, 25 A at 75°C, and 30 A at 90°C, and 240.4(D)(5) then holds the overcurrent device at 20 A, so the higher columns only help with derating. The same conductor is the Table 250.122 ground for a 20 A circuit, it never serves as a grounding electrode conductor, it drops 3% over 45 ft at 20 A on 120 V, and it fills a box at 2.25 cubic inches per counted conductor. The 12 AWG row in full.

Which insulation sits in which column

Table 310.16 names the insulation types under each column heading, so the column a conductor belongs in is decided by what is printed on the cable, not by what an installer prefers. The lists differ between copper and aluminum.

  • Copper 60°C: TW, UF. 75°C: RHW, THHW, THW, THWN, XHHW, USE, ZW. Copper 90°C: TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2. (7 types at 75°C, 17 at 90°C.)
  • Aluminum 60°C: TW, UF. 75°C: RHW, THHW, THW, THWN, XHHW, USE. Aluminum 90°C: TBS, SA, SIS, THHN, THHW, THW-2, THWN-2, RHH, RHW-2, USE-2, XHH, XHHW, XHHW-2, ZW-2. (6 types at 75°C, 14 at 90°C.)