Wire Size GuideNEC 2023 · 2026 · Updated Apr 2026

What wire size for a 45 amp circuit?

Q: What is the minimum wire size for a 45 amp circuit?

The minimum wire size is 8 AWG copper or 6 AWG aluminum per NEC 2023 Table 310.16 with 110.14(C) termination limits applied. For long runs, you may need to upsize to account for voltage drop. See the max distance table above.

Q: Can I use aluminum wire for a 45 amp circuit?

Yes. 6 AWG aluminum handles 45A. Aluminum requires anti-oxidant compound and AL-rated terminals (marked AL/CU on the device). It costs roughly 40-60% less than copper but requires a larger gauge for equivalent ampacity. See the 8 AWG copper vs aluminum comparison.

Q: How far can I run 8 AWG wire on a 45 amp circuit?

At 240V, 8 AWG copper can run approximately 102 feet before exceeding the 3% voltage drop recommendation. For longer distances, upsize to the next gauge. Use the voltage drop calculator for your exact scenario.

Q: What breaker size for a 45 amp circuit?

Use a 45A breaker. The breaker must match the circuit rating, not the wire ampacity. For continuous loads (like EV chargers), the breaker must be rated at 125% of the load per NEC 210.19(A)(1).

For a 45A circuit on a 45A breaker: Use 8 AWG copper (50A capacity) or 6 AWG aluminum (50A capacity). Common applications: medium commercial loads between 40A and 50A standard sizes.

Copper8 AWG

Aluminum6 AWG

Breaker45A

Voltage240V

All valid wire sizes for a 45 amp circuit

A 45 amp breaker is a standard size per NEC 240.6(A). It sits between the common 40A and 50A sizes. The minimum wire is 8 AWG copper for short runs, or 6 AWG for longer distances with voltage drop considerations.

45A is a standard but less common breaker size. 8 AWG copper at 50A (75°C termination limit) is adequate. For long runs, 6 AWG copper provides better voltage drop performance.

Any gauge with ampacity equal to or greater than 45A per NEC 2023 Table 310.16, after 110.14(C) termination limits are applied. Smaller gauge number means thicker wire, higher cost, but lower voltage drop.

Gauge	Material	Capacity	Max distance (3% drop)	Conduit
8 AWG (minimum)	Copper	50A	102 ft	3/4" EMT
6 AWG	Copper	65A	163 ft	3/4" EMT
4 AWG	Copper	85A	258 ft	1" EMT
3 AWG	Copper	100A	326 ft	1" EMT
2 AWG	Copper	115A	410 ft	1" EMT
1 AWG	Copper	130A	517 ft	1-1/4" EMT
1/0 AWG	Copper	150A	652 ft	1-1/4" EMT
2/0 AWG	Copper	175A	833 ft	1-1/2" EMT
3/0 AWG	Copper	200A	1034 ft	2" EMT
4/0 AWG	Copper	230A	1304 ft	2" EMT
6 AWG (minimum)	Aluminum	50A	99 ft	3/4" EMT
4 AWG	Aluminum	65A	157 ft	3/4" EMT
3 AWG	Aluminum	75A	198 ft	1" EMT
2 AWG	Aluminum	90A	250 ft	1" EMT
1 AWG	Aluminum	100A	315 ft	1" EMT
1/0 AWG	Aluminum	120A	400 ft	1-1/4" EMT
2/0 AWG	Aluminum	135A	500 ft	1-1/4" EMT
3/0 AWG	Aluminum	155A	638 ft	1-1/2" EMT
4/0 AWG	Aluminum	180A	789 ft	2" EMT

Maximum wire run distance

One-way distance in feet before voltage drop exceeds 3%, per NEC Chapter 9 Table 8 resistance values. If your run is longer than these distances, upsize one gauge.

Gauge	Material	120V	208V	240V	480V
8 AWG	Copper	51 ft	89 ft	102 ft	205 ft
6 AWG	Copper	81 ft	141 ft	163 ft	326 ft
4 AWG	Copper	129 ft	225 ft	258 ft	517 ft
3 AWG	Copper	163 ft	283 ft	326 ft	652 ft
2 AWG	Copper	205 ft	357 ft	410 ft	833 ft
1 AWG	Copper	258 ft	447 ft	517 ft	1034 ft
1/0 AWG	Copper	326 ft	566 ft	652 ft	1304 ft
2/0 AWG	Copper	410 ft	714 ft	833 ft	1666 ft
3/0 AWG	Copper	526 ft	909 ft	1034 ft	2142 ft
4/0 AWG	Copper	652 ft	1153 ft	1304 ft	2727 ft
6 AWG	Aluminum	49 ft	85 ft	99 ft	197 ft
4 AWG	Aluminum	78 ft	136 ft	157 ft	315 ft
3 AWG	Aluminum	99 ft	172 ft	198 ft	394 ft
2 AWG	Aluminum	125 ft	217 ft	250 ft	500 ft
1 AWG	Aluminum	157 ft	275 ft	315 ft	638 ft
1/0 AWG	Aluminum	198 ft	344 ft	400 ft	789 ft
2/0 AWG	Aluminum	252 ft	434 ft	500 ft	1000 ft
3/0 AWG	Aluminum	319 ft	545 ft	638 ft	1250 ft
4/0 AWG	Aluminum	400 ft	697 ft	789 ft	1578 ft

Common 45A circuit projects

commercial equipment
medium industrial motors

Frequently asked questions

What is the minimum wire size for a 45 amp circuit?

The minimum wire size is 8 AWG copper or 6 AWG aluminum per NEC 2023 Table 310.16 with 110.14(C) termination limits applied. For long runs, you may need to upsize to account for voltage drop. See the max distance table above.

Can I use aluminum wire for a 45 amp circuit?

Yes. 6 AWG aluminum handles 45A. Aluminum requires anti-oxidant compound and AL-rated terminals (marked AL/CU on the device). It costs roughly 40-60% less than copper but requires a larger gauge for equivalent ampacity. See the 8 AWG copper vs aluminum comparison.

How far can I run 8 AWG wire on a 45 amp circuit?

At 240V, 8 AWG copper can run approximately 102 feet before exceeding the 3% voltage drop recommendation. For longer distances, upsize to the next gauge. Use the voltage drop calculator for your exact scenario.

What breaker size for a 45 amp circuit?

Use a 45A breaker. The breaker must match the circuit rating, not the wire ampacity. For continuous loads (like EV chargers), the breaker must be rated at 125% of the load per NEC 210.19(A)(1).

Do I need GFCI on a 45 amp circuit?

GFCI requirements depend on location, not amperage. NEC 2023 requires GFCI in kitchens, bathrooms, garages, outdoors, basements, laundry areas, and near sinks. Check the GFCI requirements by room for your specific installation.

Common products for 8 AWG Copper circuits

🧵Wire Roll8 AWG copper, 100ftCheck prices on Amazon (paid link) ⚡40A BreakerStandard pairing for 8 AWGCheck prices on Amazon (paid link) 🔋EV ChargerLevel 2, pairs with 8 AWGCheck prices on Amazon (paid link)

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Requirements vary by state. NEC edition, licensing, permits, and GFCI rules differ by jurisdiction. Check your state or pick it below for personalized info across WireRef.

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NEC 2023 references verified April 2026