What Wire Size for 80 Amps?

Copper Wire

4 AWG

5.1894 mm · 21.1506 mm²

Aluminum Wire

2 AWG

6.5437 mm · 33.6308 mm²

Breaker: 80A · Based on NEC Table 310.16, 75°C column (needs 75°C-rated terminations)

80-Amp Wire Size by Termination Rating

Rule	Copper	Aluminum
60°C column — NM-B cable, or any termination not marked 75°C	3 AWG	1 AWG
75°C column — THHN/THWN-2 with 75°C-rated breaker and lugs	4 AWG	2 AWG

Most breakers and panelboards rated 100A or less are listed 60/75°C, but NM-B cable is always limited to the 60°C column (NEC 334.80). When in doubt, use the 60°C answer.

Common Uses for 80A Circuits

Large sub-panels, industrial feeders

4 AWG Copper — Key Specs

Diameter	5.1894 mm (0.204307")
Area	21.1506 mm²
Resistance at 20°C	0.8151 Ω/km
Weight	189.51 kg/km
Ampacity (75°C)	85 A

Important: For long wire runs, you may need to upsize the wire to compensate for voltage drop. NEC recommends keeping voltage drop under 3% for branch circuits. Use our voltage drop calculator to check.

Voltage Drop by Distance — 4 AWG Copper at 80A

One-way run	Drop	% of 240V	Verdict
25 ft	1.23 V	0.5%	Within the 3% branch-circuit target
50 ft	2.46 V	1.0%	Within the 3% branch-circuit target
75 ft	3.70 V	1.5%	Within the 3% branch-circuit target
100 ft	4.93 V	2.1%	Within the 3% branch-circuit target
150 ft	7.39 V	3.1%	Over 3% — upsize one gauge
200 ft	9.86 V	4.1%	Over 3% — upsize one gauge

Single-phase, 240V, full 80A load, 0.308 Ω/1000 ft DC resistance (NEC Chapter 9, Table 8) at 75°C terminations. NEC 210.19(A) Informational Note recommends keeping branch-circuit drop at or below 3%, and 5% total across feeder plus branch circuit. Voltage drop is a performance recommendation, not a code requirement — but exceeding it causes dim lights, slow motor starts, and wasted energy.

Aluminum Feeder Specifications

Aluminum has about 61% of copper’s conductivity, so a 80A feeder that takes 4 AWG copper needs 2 AWG aluminum — typically one to two gauge sizes larger.

Aluminum conductor	2 AWG
Ampacity (75°C, Table 310.16)	90 A
Copper equivalent	4 AWG (85 A)
Resistance	0.2402 Ω/1000 ft
Voltage drop at 100 ft, 80A	5.10 V (2.1% of 240V)

Installing aluminum correctly

Modern aluminum building wire must be AA-8000 series alloy (NEC 310.14(A)(1)). The 1960s-era AA-1350 alloy behind aluminum’s bad reputation is no longer permitted for branch circuits.
Terminate only on lugs and breakers marked AL/CU or AL9CU. Copper-only terminals are the most common failure point.
Apply an antioxidant compound to the stripped conductor before landing it, unless the termination is listed as not requiring it.
Torque every connection to the manufacturer’s value with a calibrated torque tool — NEC 110.14(D) makes this mandatory. Loose aluminum terminations are the primary cause of feeder failures.
Aluminum runs roughly half the weight and a third to half the cost of copper at feeder sizes, which is why it dominates service entrance and sub-panel feeders.

Frequently Asked Questions

What wire size do I need for 80 amps?

Using the 60°C column of NEC Table 310.16, which NEC 110.14(C) requires by default for circuits of 100A or less and always for NM-B cable, a 80-amp circuit needs 3 AWG copper or 1 AWG aluminum. With THHN/THWN-2 conductors and breakers and lugs rated 75°C, 4 AWG copper or 2 AWG aluminum is permitted.

What breaker do I need for 80 amps?

A 80-amp circuit uses a 80A double-pole circuit breaker. The breaker protects the 4 AWG copper (or 2 AWG aluminum) wire from overload. Double-pole breakers are used for 240V circuits and occupy two slots in the panel.

What wire size for an 80-amp sub-panel?

An 80-amp sub-panel feeder needs 4 AWG copper or 2 AWG aluminum with 75°C-rated terminations, or 3 AWG copper or 1 AWG aluminum if the 60°C column applies. This suits a large detached garage, workshop or accessory dwelling unit (ADU).

Can I use 4 AWG aluminum wire for an 80-amp circuit?

No. 4 AWG aluminum is rated 65A at 75°C and 55A at 60°C per NEC Table 310.16, both below 80A. Use 2 AWG aluminum (90A at 75°C) or 1 AWG aluminum if the 60°C column applies, or 4 AWG copper (85A at 75°C).

Wire size for other amperages

15A 20A 30A 40A 50A 60A 70A 100A 125A 150A 200A

Circuit breaker size chart → Wire types and insulation ratings → NEC Table 250.122 — ground wire size → 4 AWG full specifications → Full AWG chart → Wire size calculator → Ampacity tables →