Correct wire sizing is very important. Especially safety-wise. One of the most common questions we get about wiring is ‘what is the wire size for a 60 amp breaker?’.
A lot of homeowners make this very common mistake: They use 6 AWG wire for a 60 amp breaker because 6 AWG gauge wire has 65A ampacity. At first hand, that seems quite reasonable, and it’s an honest mistake to make. The problem is that we run a risk of frying our 60 amp breaker if we use the 6 AWG wire.
That’s why we’ll look at how to adequately choose a wire size for a 60 amp breaker using two National Electrical Code (NEC) CODE rules.
Knowing how to determine a 60 amp wire size will help you in any kind of situation. This may range from:
- 60 amp service wire size.
- 60 amp circuit wire size.
- Copper 60 amp wires.
- Even wire size for 60 amp sub-panel 150 feet away.
The size of the wire is always the same in theory (we’ll cover how big a wire you need for a 60 amp breaker further on):
60 amp wire size is either 6 AWG or 4 AWG wire (AWG stands for American Wire Gauge; standard wire sizing is the US) for 220V voltage. An amateur will use a 6 AWG wire size for 60 amp 220V. A professional will always use 4 AWG wire size for 60 amp 220V.
As we’ll see further on, the choice of wire size for a 60 amp breaker shouldn’t only take the ampacity of a wire into account. It’s imperative that we also use ‘Chapter 3: NEC CODE Wiring Methods and Materials‘ rules (specifically NEC 220-2 and NEC 310-16 rules), which include:
- 80% breaker rating rule. Maximum loading for any branch circuit is 80% of the rating of the circuit for the ampacity of wire for any load.
- Account for voltage drop. The rule of thumb for voltage loss dictates that if the length of the 60 amp wire is 100 feet, we will see a 20% voltage drop. That means that 4 AWG wire will not suffice; we might have to use 3 AWG wire for a 60 amp breaker at a 100+ feet distance.
Now, if you consult the AWG gauge wire size chart here, you can see that:
- 6 AWG wire has 65A ampacity.
- Bigger 4 AWG wire has 85 AWG ampacity.
Let’s look at these two rules closely. It will help illustrate why professionals always recommend using 4 AWG instead of 6 AWG for 60 amp breakers.
Note: In the end, you will be fully equipped to size any wire (including the 60 amp breaker wire size) yourself. If you’ll have any problems, you can pose a question in the comments and we’ll try our best to help you out.
80% Breaker Rating Rule For 60 Amp Wire Sizing (1st Rule)
It’s obvious why an amateur would use a 6 AWG wire for a 60 amp breaker at 220V. 6 AWG wire has a 65A ampacity, and you only need 60 amps for a 60 amp breaker, right?
Sadly, it’s not that simple.
We need to apply the most important rule in wire sizing: The 80% breaker rating rule, according to the NEC Code. This rule is to ensure electrical safety; you don’t want to fry an electrical circuit because you choose a wire gauge that’s too small.
Here is how this rule works:
Let’s say we want to determine the wire gauge for the 60 amp breaker. This can be anything from a 60 amp hot tub wire size to a wire for 60 amp service, you name it.
60 amps is 80% of the wire size you need. That means that for a 60 amp breaker, you will need a wire that can handle at least 75 amps. Here is how you make this very important calculation:
Adequate Wire Size = 60 amps ÷ 0.8 = 75 amps
This is what all those homeowners that mistakenly use 6 AWG gauge wire for 60 amp breaker don’t take into account. 6 AWG can only handle 65 amps.
Here’s what a professional will know:
The next wire size that can handle more than 75 amps (as required for a 60 amp breaker) is the 4 AWG gauge wire. 4 AWG can handle 85 amps; that’s more than enough ampacity to adequately wire a 60 amp breaker, even accounting for the 80% breaker rule.
Note: This principle also accounts for free air and direct burial wire size calculation.
In some limited cases, however, we also use a 3 AWG wire size for a 60 amp breaker. That’s because of the 2nd NEC CODE rule:
Account For Voltage Drop (2nd Rule)
If you have a short circuit, you can freely disregard the voltage loss. However, if you have a long wire connecting to a 60 amp breaker, you have to take the voltage drop into consideration.
By disregarding the voltage drop, you can mistakenly use the regular 4 AWG gauge wire when you should, in fact, be using a bigger 3 AWG wire.
Here is the rule of thumb for voltage drop that we should be using:
For every 100 feet of wire, the voltage drops by 20%.
Some factors like the choice of wire (copper, aluminum, iron, steel, etc.) and the number of wires may influence the exact percentage loss, but this is the general rule of thumb.
That means that we should increase the amps by 20% for every 100 feet of wire if we are to get the same power output (wattage) according to the basic electric power equation:
Power (Watts) = Current (Amps) × Voltage (Volts)
Let’s use an example to showcase what a voltage drop is and how to calculate the wire size for a 60 amp breaker that’s some distance from the power source.
Example: What is a wire size for a 60 amp sub-panel 150 feet away?
Alright, using the 80% breaker rating rule, we already know that we need a wire that can handle at least 75 amps. Now, we have to add the amps in order to balance out the voltage drop.
According to the rule of thumb for voltage loss, in 150 feet of wire, we lost 30% of voltage (100 feet = 20%, 150 feet = 30% loss). That means we have to increase the amps by 30%. Here’s how we calculate the final amps:
75 amps × 1.3 = 97.5 amps
This means that a wire for a 60 amp sub-panel 150 feet away must handle at least 97.5 amps. 6 AWG wire can handle 65 amps, 4 AWG wire can handle 85 amps. In this case, due to 150 feet distance, both of these wires have a too low amperage.
We need the next wire size: 3 AWG. This wire size can handle up to 100 amps. It’s perfect in this case.
In short, the wire size for a 60 amp sub-panel 150 feet away is 3 AWG gauge wire.
Now You Know How To Determine Any Wire Size
It’s notoriously easy to make mistakes when sizing wires and it’s not uncommon to see 60 amp breakers go up in flames as a result.
With these two simple NEC CODE rules – 80% breaker rule and voltage drop rule – you can adequately size a wire like a professional.
Hope this was helpful and will help you make the right choice for the size of your 60 amp breaker.
This was an extremely helpful article. Thank you so very much!
thank you guys and lady’s who post things like this it makes things so much easier to find the truth about wiring problems thanks again.
Thank you for the lesson. Very clear and informative.!!
Thankful for important information!!!
KUDOS 🙏🏼🙏🏼🙏🏼
Question: You are applying an 80% rule for the wire amp rating vs. the breaker amp rating, BUT what about the fact that the appliance’s current draw is already only 80% of the max breaker amps?
If I’m running an appliance that draws 48 amps and I installed a dedicated 60-amp breaker (following the 80% rule) then why does the wire have to handle more than 60 Amps if I’m only running a 48 amp current through that wire?
Bottom line, can I safely use a 6-gauge copper wire (about 30-40 feet in length) with a 60-amp breaker if the appliance only draws 48 amps. The “appliance” in this case is a home installation of an electric car charging station.
Hello Saty, your thinking is correct. 60 amp breaker should be installed if you want 48A current. To carry that current, you also need a wire that can handle 60A; after 80% rule, it can carry 48 amps. Hope this makes sense.
“then why does the wire have to handle more than 60 Amps if I’m only running a 48 amp current through that wire? “ it wouldn’t. 6awg copper is fine for a 48a car charger. 6awg THHN is good for 65 amps and a 60amp breaker will trip at 48amps. Breakers an fuses are engineered weak links. They’re designed to protect the wires, not the other way around. The 80% rule only applies to the breakers requiring you to not load in beyond 80% of its rating.
Exactly. That is what jumped out to me and is not clear in this article. I agree with the majority of what is said but if you’re limited to 48 amps for a level II charger, then a 60 amp breaker and 6g wire should be perfectly OK. Please let me know if I’m wrong.
Regardless, I am going to install a new sub panel to supply 120 V and 240V for a level II charger and a 30A 120V feed to my motor home. And I will use 4g, just because there is no harm in over building.
How about somebody that looks at your circuit and sees a 60 amp breaker and hooks up a appliance that draws 60 amps and thinks it all good? The rules are to protect everybody, not yout you and your 48 amp load.
Ok so now we’re playing the what if game. Come on Graham, Saty13 is 100% correct. He needed a circuit that was safe to code and proper power to charge a car. All the correct mathematical equations were made. He needs a 48 amp circuit and wires for a 60amp circuit. Wish most homeowners did there DIY projects like this. Would save me a lot of time on tripping breaker calls lol
The 60 Amp breaker is good for preventing incidental trips and overheating of the breaker since it is 20% over the sustained 48 Amp intended usage, but after that, it needs to be the weakest link in the circuit to serve its intended purpose of protecting from fires, etc. Even if the wire will handle the same peak load as the breaker, it is safer if the wire handles 20% over the breaker so that the wire won’t overheat and start a fire in things like drywall before the breaker trips in the event of a fault or accidental short (think nail through the wire type thing). 6 AWG might be okay for a short run, but 4 AWG definitely will be okay.
I have a dedicated hardwired EV charger (EVSE), The EVSE is rated at 40 amp max but the cars onboard charger never draws more than 32 amp. Currently it has a new 50 amp breaker and 6AWG wire that is about 12′ in length from the panel to the EVSE. The amp breaker trips under 32 amp because of the Texas heat and the wall where the electric panel and fuse located is facing south. The breaker trips because of ambient temps and radiating heat. If this is a dedicated circuit to the car’s charging equipment, can I safely use a 60 amp breaker? thanks
Hi Charley, if the 50 amp breaker is tripping, installing a 60A or two 30A breakers would make sense.
If I have a 60 amp plug and use a 60 amp cord, can I connect to a dryer that only needs a 30 amp
Hi Betty, of course, drier has a 30 amp draw and your circuit can handle 60 amps.
Thank you for the article. Very well written and detailed. I’m planning to install an EV charger, 100 feet away from my main panel. Planning to use a 60amp breaker (for a maximum of 48amp output from the charger). According to your calculations I would need a wire that can handle 90amp, correct? If so, can I use a 4awg wire for that? Thanks.
Hi Sharon, thank you. Yes, the 4 AWG wire will be adequate for this situation.
I am installing a hot tub in my backyard it’s 65 feet from the breaker I need a 240v 60amp is a 4AWG wire good or should I use a 3AWG ? Thanks Claude
Hi Claude, the 4 AWG copper wire has a median ampacity of 85A. That will be more than sufficient for a 60 amp service 65 feet away. No need for the 3 AWG wire.
To add a bit: if you are making a dedicated circuit for something like an EV charger (L2 EVSE) your best bet is to look at the documentation from the manufacturer. That will always override general code requirements. For instance, my 48A Tesla Wall Connector is installed on a 60A breaker and fed by 6AWG because that’s what Tesla says in their manual.