What Size Wire for a 60 Amp Breaker?

Use 6 AWG copper for a 60 amp breaker when the terminals are rated 75 °C (65 A). Use 4 AWG copper when the terminals or cable are limited to 60 °C, including NM cable. Aluminum needs 4 AWG.

The answer

4 AWG copper

for NM (Romex) cable or 60 °C terminals

6 AWG copper

THHN in conduit with 75 °C terminals

4 AWG aluminum (75 °C terminals)

Wire size for a 60 amp breaker
Case Wire size Table ampacity Area
Copper · 75 °C THHN in conduit, most modern equipment 6 AWG 65 A 13.3 mm²
Copper · 60 °C NM / Romex cable, older terminals 4 AWG 70 A 21.2 mm²
Aluminum · 75 °C Needs connectors and terminals listed for aluminum 4 AWG 65 A 21.2 mm²

Calculate for your exact distance

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How the answer is worked out

The breaker is 60 A. The smallest copper wire with a 75 °C table ampacity at or above 60 A is 6 AWG, rated 65 A, with a cross-section of 13.3 mm².

For 60 °C terminals or NM cable the smallest copper size is 4 AWG, rated 70 A in the 60 °C column.

Aluminum uses its own column. The smallest aluminum size at 75 °C for this rating is 4 AWG, rated 65 A. Aluminum conductors need connectors and terminals listed for aluminum.

NEC 240.4(D) also limits the breaker for small conductors: 14 AWG copper is capped at 15 A, 12 AWG copper at 20 A, 10 AWG copper at 30 A, 12 AWG aluminum at 15 A and 10 AWG aluminum at 25 A. The sizes in the table respect those caps, so a wire is never paired with a breaker larger than its limit.

Why the terminal rating matters

6 AWG copper is rated 55 A in the 60 °C column but 65 A in the 75 °C column. Most modern breakers and panels have 75 °C terminals, so 6 AWG is enough. If any termination or the cable itself is limited to 60 °C, as with NM cable, you must use 4 AWG (70 A).

Subpanels and feeders

A 60 amp subpanel feeder serving a detached garage or workshop is common. Check that the feeder wire, the breaker and the subpanel lugs are all rated for the temperature you are using, and size the feeder for voltage drop if the building is far from the main panel.

Aluminum

Aluminum 4 AWG is rated 65 A at 75 °C, so it is the smallest aluminum feeder for a 60 amp breaker.

How far can you run it? (3% voltage drop)

The distance table uses the same resistance-only model as the calculator, with a 3% limit and the wire at 75 °C. Aluminum has about 1.6 times the resistance of copper for the same size, so an aluminum run of the same length drops more voltage.

Assumes the full 60 A load on a single-phase 240 V circuit, a 75 °C conductor, copper or aluminum, a 3% voltage drop limit and the one-way length in the table. Aluminum shows a dash where that size cannot carry the full current.

Maximum one-way length for 3% drop at 60 A, 240 V, 75 °C conductor
Wire size Copper Aluminum
6 AWG 122.4 ft [37.3 m] —
4 AWG 194.7 ft [59.3 m] 118.2 ft [36.0 m]
3 AWG 245.5 ft [74.8 m] 149.1 ft [45.4 m]
2 AWG 309.5 ft [94.3 m] 188.0 ft [57.3 m]

Need a specific distance? See: What Size Wire for a Subpanel Feeder?

Before you buy wire

The table is a starting point. Work through this list before you order conductors, and keep the answer that matches your real installation.

This is general information based on NEC tables, not a permit or an installation plan. Local amendments, the equipment nameplate and an inspector decide what is acceptable. Read the disclaimer.

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