4 Gauge/AWG Wire: 4/2 Wire, 4/3 Wire, and 4/4 Wire

4 gauge wires are relatively thick wires that are seldom used at home and residential electrical installations but may be quite common in light industrial applications and applications that require currents in the 50-60 Amps range.

4 gauge wires differ in wire material, construction, Ampacity, and a few other details, making it very important to choose the very best 4 gauge wire carefully.

Published: September 16, 2022.

 4 Gauge/AWG Wire Thickness

American Wire Gauge (AWG) 4 wire may be made of solid or stranded wire, made of pure copper, aluminum, Copper Clad Aluminum (CCA), and a few other materials that are very rarely used (for example, oxygen-free copper and similar).

The physical dimensions of the solid copper 4 gauge wire are:

- Diameter: 5.1894 mm, 0.2043 inches,

- Cross Section: 21.1506 mm2, 0.0328 inches2.

Since stranded wires feature air gaps between the individual strands (~20-25% of the stranded wire is actually - air), the diameter of the stranded wires with the same Ampacity (wire current carrying ability) is ~12-14% larger than the diameter of the solid wire (~6 mm on average).

However, solid 5-6 mm copper wire is not easy to work with, making this 12-14% difference mostly negligible for many applications (for example, welding wire).

4 AWG Copper Wire vs. 4 AWG Aluminum Wire

As a wire material, aluminum is lighter and cheaper, but it also features larger electric resistance than copper.

Also, as the aluminum wire warms up, it expands more than the copper wire.

So, for many applications, copper 4 gauge wires are the preferred choice over aluminum 4 gauge wires.

If we check the Ampacity of the 4 gauge solid copper wire, then we can see that the actual Ampacity depends on the maximum allowed surface temperature:

• @60°C/140°F: 70 Amps,
• @75°C/167°F: 85 Amps,
• @90°C/194°F: 95 Amps.

On the other hand, the Ampacities of the 4 gauge solid aluminum wire are:

• @60°C/140°F: 55 Amps,
• @75°C/167°F: 65 Amps,
• @90°C/194°F: 75 Amps.

This 15-20 Amps difference is a serious difference, showing why the copper is preferred choice as wire material over aluminum, at least for the applications where wire weight is not that important.

These are the default Ampacities of the solid 4 gauge copper and aluminum wires, and these values don't include any safety margin - time for "Rule 80%".

80% Rule

The 80% Rule is a very important safety rule which says that the actual Ampacity of the wire is 80% of its nominal/default value.

Thus, we can write:

Since @60°C/140°F is the maximum allowed surface temperature for many applications, we can say that 4 AWG copper wire can safely handle 56 Amps, while 4 AWG aluminum wire can safely handle 44 Amps.

And this is just for relatively short wires. If the wires are longer, the actual capacity drops by 10% for every 50 feet (~15.25 m) of wire.

For example, the actual Ampacity for a 100 feet long 4 gauge wire with the maximum allowed surface temperature of 60°C/140°F would be:

Ampacity = 70 * 0.8 / 1.2 = 46.66 Amps

The following chart lists the Ampacity (given in Amps) of 4 gauge copper wire at default temperatures for the wires of 50, 100, 150, and 200 feet long.

Since the maximum allowed temperature for residential use is 60°C/140°F, the second column shows the actual Ampacity (current carrying ability) of 4 gauge wire depending on its length.

A similar calculation can be done for the 4 gauge aluminum wire.

4 AWG Wire Cables: 4/2 Wire, 4/3 Wire, and 4/4 Wire

Regardless of their thickness, wires are rarely used individually - they are most often arranged in cables consisting of two or more wires.

Hence, cables can be labeled as 4/2 Wire (4 2 Wire), 4/3 Wire (4 3 Wire), and 4/4 Wire (4 4 Wire) - cables with more wires are generally rare and are often custom built.

When the cable is labeled as, for example, "4/3 Wire", that means that it is a cable consisting of three 4 gauge wire conductors and one ground wire. Thus:

• "4/2 Wire" or "4 2 Wire," consists of two 4 gauge wire conductors and one ground wire.
• "4/3 Wire" or "4 3 Wire," consists of three 4 gauge wire conductors and one ground wire.
• "4/4 Wire" or "4 4 Wire", consists of four 4 gauge wire conductors and one ground wire.

Note: 4/0 wire is 0000 AWG (four "zeros") or 0000 gauge wire and NOT 4 gauge wire with zero conductors - that wouldn't have much sense, right?

To help users connect wires correctly when assembled in cables, wires are color coded.

Frequently Asked Questions

Here are some of the most common Frequently Asked Questions about 4 AWG/gauge wires and electrical wires in general:

How thick is 4 gauge wire?

The physical dimensions of the solid 4 gauge wire are:

• Diameter: 5.1894 mm, 0.2043 inches,
• Cross Section: 21.1506 mm², 0.0328 inches².

Note that stranded copper wires feature a diameter that is 12-14% larger due to the air gaps between individual strands.

Also, aluminum 4 gauge wires share the same dimensions, just their Ampacity is lower.

How many Amps can 4 gauge wire handle?

Actual Ampacity depends on the wire material (copper, aluminum) and length.

For example, 4 AWG 50 feet long copper wire can safely handle 50.90 Amps with the maximum allowed surface temperature of @60°C/140°F.

Note:  the average person can hold a @60°C/140°F object for 4-6 seconds before it must be dropped out of hands due to the heat.

What is 4 gauge wire used for?

4 gauge wire is often used in applications that require wire that can safely handle 50-60 Amps max and, as such, is rarely used in residential applications.

A typical example of 4 gauge wire use are cables for electric welding, cables for larger electric trolling motors, inverter battery wires, and similar.

Where to buy 4 gauge wire locally?

If You want to buy 4 gauge locally, check local hardware stores and stores that sell electric equipment and supplies.

If You are unable to find proper wires, try online shops - with fast deliveries, You may have your wire within 24-48 hours.