2023 NEC · Table 310.16

3 AWG copper wire ampacity

At a 75°C termination rating, 3 AWG copper carries 100 A under the published table's basis conditions - 30°C ambient, no more than three current-carrying conductors.

NEC 2023Every ampacity below is transcribed from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

Ampacity by temperature rating

3 AWG copper, at a 30°C ambient with no more than three current-carrying conductors in a raceway or cable. The 90°C column is normally used only as the starting point for derating.
Temperature rating	Ampacity	Typical insulation
60°C	85 A	-
75°C	100 A	THW
90°C	115 A	THHN / THWN-2, XHHW-2

What 3 AWG copper is used for

3 AWG copper carries 100 A at 75°C, putting it in feeder and subpanel territory - detached garages, workshops, and service upgrades. It pairs with a 100 A overcurrent device.

Terminations usually decide the practical answer. Breakers and equipment are typically listed for 60°C or 75°C, so even 90°C-rated insulation on this conductor is normally limited to the 100 A column at the terminals. Check the equipment's listing rather than assuming.

Derating

Ampacity in real conditions

NEC 2023Every derated value in this table is transcribed from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

3 AWG copper at a 75°C termination rating, corrected for ambient temperature and adjusted for the number of current-carrying conductors, then capped by any small-conductor limit. Adjustment factors: 4-6 → 80%, 7-9 → 70%, 10-20 → 50%.
Ambient	3 conductors	4 conductors	7 conductors	10 conductors	21 conductors
20°C	111 A	88.8 A	77.7 A	55.5 A	50 A
30°C	100 A	80 A	70 A	50 A	45 A
40°C	88 A	70.4 A	61.6 A	44 A	39.6 A
50°C	75 A	60 A	52.5 A	37.5 A	33.8 A

NEC 2023Every property and drop figure below is transcribed from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

Properties

Circular mils	52,620
DC resistance	0.245 Ω per 1000 ft
Ampacity at 75°C	100 A
Overcurrent ceiling	Set by ampacity
Largest standard breaker	100 A
Area, THHN / THWN-2	0.0973 in²
Area, XHHW-2	0.0962 in²
Area, THW	0.1134 in²

Voltage drop over distance

Single-phase 240 V, carrying 100 A on 3 AWG copper.

Circular-mil estimate at full load. Lighter loads drop proportionally less. Use the voltage drop calculator for your actual current.
One-way distance	Drop	Within 3%?
25 ft	0.51%	Yes
50 ft	1.02%	Yes
100 ft	2.04%	Yes
150 ft	3.06%	No
200 ft	4.09%	No
300 ft	6.13%	No

FAQ

Frequently asked questions

How many amps can 3 AWG copper wire carry?

100 A at a 75°C termination rating under 2023 NEC Table 310.16, at the table's basis conditions of a 30°C ambient and no more than three current-carrying conductors. The 60°C column reads 85 A and the 90°C column 115 A, but terminations on breakers and equipment usually hold the practical answer to the 75°C column.

What size breaker goes with 3 AWG copper wire?

100 A is the largest standard rating at or below the 100 A this conductor is good for at 75°C under the 2023 NEC. A hotter location or a fuller raceway derates the conductor and can push the breaker down; the derating table above shows how far.

Does 3 AWG copper ampacity change with heat or bundling?

Yes. The published 100 A assumes a 30°C ambient and at most three current-carrying conductors in the raceway or cable. At a 40°C ambient with seven current-carrying conductors, the same 3 AWG copper conductor is usable at 61.6 A after the 2023 NEC correction and adjustment factors. The derating table above covers more combinations.

How far can 3 AWG copper wire run before voltage drop is a problem?

Carrying its full 100 A on a 240 V single-phase circuit, the circular-mil estimate this page uses stays inside a 3% drop out to about 146 ft one way, and reads 0.51% at 25 ft. Lighter loads drop proportionally less. The 2023 NEC treats 3% as a recommendation for efficient operation, not a general requirement.

Source: NFPA 70, National Electrical Code, Table 310.16; NFPA 70, National Electrical Code, Table 310.15(B)(1)(1); NFPA 70, National Electrical Code, Table 310.15(C)(1); NFPA 70, National Electrical Code, Chapter 9, Table 8. Published by NFPA.NEC 2023Transcribed from the 2023 NEC (NFPA 70, 2023). Confirm against your locally adopted edition and your authority having jurisdiction (AHJ).

Nearby conductors

4 AWG copper 2 AWG copper 3 AWG aluminum 100 A breaker wire size Wire size calculator Ampacity lookup

Every figure on this page comes from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

Reference estimate - verify before you build. AmpSizer reports reference estimates transcribed from published tables in the 2023 NEC (NFPA 70, 2023), and from no other edition. It is not a substitute for the code adopted in your jurisdiction. The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build. Final conductor sizing, overcurrent protection, and installation must be determined by a licensed electrician and approved by your AHJ.

Jurisdictions adopt editions on their own schedule and frequently amend them, so the edition enforced where you work may not be the one cited here. Confirm which edition and which local amendments apply to your job before relying on any value on this page.