How many amps can 12 gauge wire carry?

12 AWG copper wire carries 20 A at 60 °C, 25 A at 75 °C and 30 A at 90 °C. 12 AWG copper goes on a breaker of up to 20 A in NM-B cable.

12 AWG wire ampacity

12 AWG copper and aluminum ampacity at 60, 75 and 90 °C, up to three current-carrying wires at 30 °C (86 °F) ambient, with the largest breaker at 75 °C and the rating as an extension cord
Rating	Copper	Aluminum
60 °C, NM-B	20 A	15 A
75 °C	25 A	20 A
90 °C	30 A	25 A
Max breaker, 75 °C	20 A	15 A
As a cord	25 A	—

Copper
Aluminum

12 AWG ampacity by temperature rating.

12 AWG copper may be protected by a breaker of no more than 20 A, whatever its ampacity column says.

12 AWG wire size and resistance

12 AWG bare conductor size and copper resistance at operating temperature. The diameter is the nominal AWG value; stranded wire of the same size is slightly larger.
Diameter, AWG nominal	0.0808 in. / 2.05 mm
Area	6,530 cmil / 3.31 mm²
Copper resistance	1.975 Ω per 1,000 ft

How far can 12 AWG wire run?

Longest one-way 12 AWG copper run within 3% voltage drop, at the full 20 A breaker load and at half load, at 120 and 240 V
Load	120 V	240 V
20 A	45 ft	91 ft
10 A	91 ft	182 ft

How many 12 AWG wires fit in conduit

Maximum number of 12 AWG THHN wires by conduit type and trade size, at 40% fill for three or more wires
THHN in	1/2″	3/4″	1″
EMT	9	16	26
PVC Sch 40	8	15	25
PVC Sch 80	6	12	20
RMC	9	16	26

What 12 AWG wire is used for

Kitchen, bathroom, laundry and garage outlet circuits
Heavy-duty extension cords

Check a 12 AWG circuit

What are you sizing for?

Breaker or load

One-way distance

From the panel to the load, not there and back

Voltage

Conductor

Termination rating

Result

12 AWG copper

Ampacity sets the size; the voltage drop is within 3%.

Breaker: 20 A
Voltage drop: 2.0 V (1.6%)
Volts at the load: 118.0 V
Ground wire: 12 AWG copper

How it is calculated

Breaker: 20 A rounded up to a standard size = 20 A.
Smallest copper conductor rated for 20 A at 60 °C: 12 AWG.
Drop = 2 × K × 20 A × 25 ft ÷ 6,530 cmil = 1.98 V, target 3% of 120 V.

Sources

7 published documents, checked on 2026-11-13

NFPA 70, National Electrical Code (2023): Allowable ampacities of insulated conductors, Table 310.16
NFPA 70, National Electrical Code (2023): Overcurrent protection of small conductors, Section 240.4(D)
NFPA 70, National Electrical Code (2023): Conductor properties, Chapter 9 Table 8
NFPA 70, National Electrical Code (2023): Ampacity of flexible cords and cables, Table 400.5(A)(1)
NFPA 70, National Electrical Code (2023): Percent of cross section of conduit and tubing for conductors, Chapter 9 Table 1
NFPA 70, National Electrical Code (2023): Dimensions and percent area of conduit and tubing, Chapter 9 Table 4
NFPA 70, National Electrical Code (2023): Dimensions of insulated conductors, Chapter 9 Table 5

Compared with 13 published documents, last on 2026-11-13

American Wire Group (edition not stated): Allowable Ampacities of Insulated Aluminum or Copper-Clad Aluminum Conductors — Aluminum columns and the 15/25 A aluminum small-conductor limits
Carlon / Thomas & Betts (ABB) (catalog (edition not stated)): General information: wire fill based on Chapter 9 Table 1 — Conduit fill percentages
Cerrowire (NEC 2017): Ampacity Charts — Copper 60/75/90 °C and aluminum 75/90 °C, 14 AWG to 600 kcmil
Florida International University (course notes, NEC edition not stated): Chapter III, Electrical Wiring Components (Figure 3.18, area of THHN conductors) — THHN areas for 14 to 6 AWG; the larger sizes match a training reproduction of the same table
LugsDirect (NEC 2020): Ampacities of Insulated Conductors From NEC Table 310.16 — All columns, copper and aluminum, every size on this site
LugsDirect (AWG formula): AWG Wire Chart, kcmil and Metric Wire Sizes — Circular mils, square millimeters and diameters by size
Michigan State University, Biosystems and Agricultural Engineering (NEC edition not stated): Electrical Tech Note 212: Conductor Properties — Conductor area, dc resistance at 75 °C and the K constants
Omni Cable (NEC 2017): NEC Ampacity Data — All columns, copper and aluminum
Southwire Company, Power Cable Installation Guide (2005 (cites 2005 NEC)): Dimensions and percent area of conduit and tubing, Table 8 (EMT, rigid PVC Schedule 40 and 80) — Fill percentages and internal areas of EMT, PVC Schedule 40 and Schedule 80
Southwire (NEC 2023): SPEC 10003, THHN/THWN-2 building wire — 14–10 AWG copper and the 15/20/30 A small-conductor limits
Southwire (NEC 2023): SPEC 45007, aluminum XHHW-2 building wire — Copper small-conductor limits 15/20/30 A
Southwire (NEC 2023): SPEC 70126, SJOOW portable cord — Cord ampacity, 18–10 AWG, two current-carrying conductors
Wheatland Tube (2022): Rigid Metal Conduit Submittal Sheet, weights and dimensions — Rigid metal conduit inside diameters; the areas follow from them

Calculated by Calculate.diy with the method of the National Electrical Code® (NEC®), 2023 edition; not the NEC text. Methodology. For planning only: check local code and use a licensed electrician.