60 Amp Wire Size - How to Calculate Proper Wire Gauge

60 Amps is a serious current, regardless if it is used to power 12V or 24V electric trolling motors or it is used in 120/230V electric systems to power homes, RVs, workshops, and similar.

When calculating proper wire thickness, there are a few important things to consider. But, whatever You do, safety first. And don't go cheap - going cheap with such currents can easily sooner or later backfire.

AWG Wire Sizes Chart

In order to pick the right wire thickness, one must check the "Ampacity" (wire current carrying capacity) of the wire, the length of the wire, and the maximum surface wire temperature.

The following comparison chart lists AWG wire sizes with their most important features:

One can't have "too thick" wire for a certain current - thicker cables mean less energy losses, but also such wires are more expensive, more difficult to work with, and similar.

Calculating the Right Wire Gauge

When looking for the right wire thickness for the required current (60 Amps), first we have to find the proper wire thickness at the required wire surface temperatures as listed in the given chart.

When calculating wire thickness, there are a few rules that one must obey, including:

- wire temperature: Wire thickness is very often calculated for temperatures of 167°F (75°C), but 140°F (60°C) is already a hot enough temperature to prevent an adult to hold the cable with an unprotected hand for more than a five-six seconds. Choosing a lower temperature adds an additional safety level.

- Ampacity or "80% Rue": when calculating wire size, we will go for the wire that features an actual Ampacity 25% better than the Ampacity in the chart. For example, when calculating wire thickness for 60 Amps, we will look for the cable with the Ampacity of:

Ampacity = 60 Amps / 0.80 = 75 Amps

So, for a 60 Amps wire, we will choose the wire size with the Ampacity of AT LEAST 75 Amps and the required temperature.

If we check the wire chart, we should find a wire with an Ampacity value of 75 Amps or the next best thing:

T = @60°C/140°F) → Ampacity = 85 Amps → AWG 3

T = @75°C/167°F → Ampacity = 85 Amps → AWG 4

T = @90°C/194°F → Ampacity = 75 Amps → AWG 6

As one can see, different maximum temperatures also mean different wire sizes. While some electricians may consider AWG 3 wire an overkill for a 60 Amps current, especially if the wires are not extra long, most will go for AWG 4 wire for 60 Amps current.

Obviously, AWG 6 for 60 Amps current is simply a too thin wire that will overheat easily every time it is pushed to its limit - not a good choice.

So, for short, we can safely say:

60 Amps wire size → AWG 4 or AWG 3 wire

without taking into account the wire length.

- Wire Length: in order to keep the energy losses to a minimum, the longer the cable, the thicker its wires should be.

There are several rules and standards that may be used when calculating the required wire thickness, but the simplest one is to add 10% for every 50 feet (~15 m) of the wire length.

For example, when calculating the required Ampacity for the 50 feet, 100 feet, and 150 feet wires, we can use (default value is 75 Amp, after applying the "80% Rule"):

50 feet wire: Ampacity = 75 Amps * 1.1 = 82.5 Amps

100 feet wire: Ampacity = 75 Amps * 1.2 = 90 Amps

150 feet wire: Ampacity = 75 Amps * 1.3 = 97.5 Amps

Now, we have to check the required AWG value for given wire lengths, depending on the wire surface temperature - values are given in the following chart:

In most situations, when calculating wire Ampacity, one uses 75°C/167°F maximum wire surface temperature meaning that for the 60 Amps current one should use either AWG 4 wires (up to 50 feet) or AWG 3 wires (up to 150 feet).

Calculating wire Ampacity for 90°C/194°F is simply not safe, while using wire thicknesses for 60°C/140°F adds an additional layer of safety, but it also increases the wire thickness, expenses, etc.

AWG 3 vs. AWG 4 Wire

The following comparison chart lists some of the most important features of the AWG 3 and AWG 4 wires:

The difference between AWG 3 and AWG 4 wires is not large in terms of thickness - looking at their cross-sections it is sometimes even hard to spot the actual difference in size between AWG 3 and AWD 4 wires, but it is there and because of it, AWG 3 wires are able to transfer more power.

Note: Never, but really never use thinner cables than required - for example, don't go for AWG 6 wires (or thinner) for 60 Amp circuits.

60 Amps Circuit Breaker

When looking for a proper circuit breaker, finding proper amperage if the circuit breaker is very simple - for a 60 Amps circuit, one needs 60 Amps electric breaker.

Unlike wires, which can be somewhat thicker, for a 60 Amps circuit, one should NEVER use a stronger circuit breaker. Also, weaker electric circuit breakers may trip too often, so, they are not recommended either.

Note: if You are unsure, contact a local certified electrician for more information, including local laws and regulations.

Types of Cables Used for 60 Amp Applications

When dealing with electrical wiring for 60 amp applications, selecting the appropriate cable type is essential for safety, efficiency, and compliance with electrical codes. Cables designed for 60 amp circuits are typically used in larger installations, such as feeding sub-panels, large machinery, and heavy-duty appliances. Here are the common types of cables suitable for such applications:

• Non-metallic Sheathed Cable (NM-B): This is one of the most common residential wiring cables, known for its ease of use and versatility. For 60 amp circuits, the typical specification would be 6/3 NM-B cable, which indicates a six-gauge wire with three conductors and a ground. This type of cable is encased in a non-metallic sheath that provides some resistance to moisture and flame. It's suitable for dry, indoor environments like basements or interior walls.
• Underground Feeder (UF) Cable: UF cable is a type of non-metallic cable designed specifically for wet locations and direct burial without the need for conduit. This makes it ideal for running external power to garages, outdoor lighting, or garden sheds. For 60 amp applications, a UF cable of six-gauge is typically recommended. It is similar to NM-B cable in construction but has a more robust and water-resistant outer sheath.
• Armored Cable (AC) or Metal Clad (MC) Cable: These cables are suited for areas where the cable might be exposed to mechanical damage. They are encased in a flexible metal sheath which provides an extra layer of protection. For 60 amp applications, six-gauge wires are also used in AC or MC cables. These are often used in industrial environments or in areas of residential construction where additional protection is necessary.
• THHN/THWN Wire: When conduit is used, THHN (thermoplastic high heat-resistant nylon-coated) or THWN (thermoplastic heat and water-resistant nylon-coated) wires are common choices. These wires are pulled through a conduit system, providing a highly secure and protected pathway. For 60 amp service, six-gauge THHN or THWN wires are necessary. This type of wiring is often seen in both residential and commercial settings for external or exposed installations.
• Photovoltaic wire (PV): PV wire is specifically designed for use in solar panel arrays and related applications within solar energy systems. It is built to handle the harsh environments typically encountered in outdoor solar installations, including exposure to UV light, extreme temperatures, and various weather conditions.

Each of these cable types has its specific applications and environments where it excels. Ensuring compliance with local electrical codes is crucial; these codes will often dictate the type of cable required based on the application's specific conditions and safety requirements.

Additionally, always ensure that any electrical installation or modifications are performed by a qualified electrician to maintain the safety and integrity of the electrical system.

Long Story Short: When looking for a 60 Amp wire, go for AWG 3 Copper Wires or AWG 4 Copper Wires (Amazon links, open in the new windows), depending on the length of the cables.

For shorter cables, AWG 4 wire may be used for shorter wires, but for anything longer, one should use AWG 3 wires or maybe even thicker.