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.
Published: May 2, 2022.
On This Page:
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:
|Wire Length / Surface Temperature||@60°C/140°F||75°C/167°F||90°C/194°F|
|<50 feet (75 Amps)||AWG 3 (85 Amps)||AWG 4 (85 Amps)||AWG 6 (75 Amps)|
|50 feet (82.5 Amps)||AWG 3 (85 Amps)||AWG 3 (85 Amps)||AWG 4 (95 Amps)|
|100 feet (90 Amps)||AWG 2 (95 Amps)||AWG 3 (100 Amps)||AWG 4 (95 Amps)|
|150 feet (97.5 Amps)||AWG 1 (110 Amps)||AWG 3 (100 Amps)||AWG 3 (115 Amps)|
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).
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:
|Wire Thickness||AWG 3||AWG 4|
|Diameter||0.2294 inches (5.8273 mm)||0.2043 inches (5.189 mm)|
|Area||0.0413 inches2 (26.6705 mm2)||0.0308 inches2 (21.1506 mm2)|
|Ampacity @60°C/140°F||85 Amps||70 Amps|
|Ampacity @75°C/167°F||100 Amps||85 Amps|
|Ampacity @90°C/194°F||115 Amps||95 Amps|
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.
Long Story Short: When looking for a 60 Amp wire, go for AWG 3 or AWG 4 copper wires, 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.