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What size wire do I need to run 50 amps 100 feet?

In most cases, 6 AWG is an almost perfectly-sized wire for a 50 amp breaker. In limited cases, you will probably have to use a larger 4 AWG wire. That's when you have a long circuit and are sending electrical current at some distance (100 feet or more).

learnmetrics.com - 50 Amp Wire Size Details: Gauge, Breaker, 220/240V Example

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50 amp is one of the most common amperages we need a gauge, breaker, or a wire for. The key questions regarding the 50 amp wire include: What is a wire size for 50 amps 240 volts? (50 amp wire gauge; NEC code applies) Wire size for 50 amp sub panel 100 feet away? (Here we will have to account for voltage loss) What electric devices can you run with a 50 amp wire? (Wattage will depend on voltage)

Let’s first clear the AWG wire gauge size:

If you check the wire gauge ampacity chart here, you can see that there are 3 AWG wire sizes that have ampacity near 50 amps. These are:

8 AWG wire with 50A ampacity (too small).

6 AWG wire with 65A ampacity (just right).

4 AWG wire with 85A ampacity (too big).

Now, choosing the 8 AWG wire with 50A ampacity seems like a good choice as a 50 amp wire size, right? However, in almost all cases, the correct 50 amp wire size is 6 AWG with 65A ampacity. That is true for any voltage; 12V, 110V, 115V, 120V, 220V, 240V, you name it.

Why is that?

We have to account for the 80% breaker rating rule, set by National Electrical Code (NEC) rules. Maximum loading for any branch circuit is 80% of the rating of the circuit for ampacity of wire for any load. Let’s have a quick look at how you can choose the right AWG gauge wire for 50 amps (or any amps for that matter). Later on, we will also look at when 6 AWG wire is not adequate as a 50 amp wire (due to voltage loss at a distance), and what you can run with a 50 amp 110V or 220/240V circuit:

50 Amp Wire Size (Using NEC 80% Rule)

You can’t use 50A ampacity wire to create a 50 amp electric circuit. If you do that, you will likely fry the circuit. The 80% rule serves as a safety measure. You should at least have that extra 20% on top of 50A ampacity.

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Here is how you calculate at least how much ampacity should a 50 amp wire have:

Wire Ampacity For 50 Amps = 50A / 0.8 = 62.5A Wire

That means that you should use a wire that can handle 62.5A as a 50 amps wire. Now, we don’t have 62.5A wire. The closest wire we have is the 6 AWG wire with 65A ampacity. Note: You can always use a bigger wire but never a smaller wire. For 50 amps, you could use 4 AWG wire with 85A ampacity (a bit of overkill but it’s OK), but you can never use 8 AWG wire with 50A ampacity (you will fry the circuit). In most cases, 6 AWG is an almost perfectly-sized wire for a 50 amp breaker. In limited cases, you will probably have to use a larger 4 AWG wire. That’s when you have a long circuit and are sending electrical current at some distance (100 feet or more).

50 Amp Wire Size 100+ Feet Away (Account For Voltage Drop)

Even you’re sending electricity through a long distance (for example, to a 50 amp sub panel 100 feet away), you have to account for voltage drop.

A good rule of thumb for voltage drop is this:

For every 100 feet, voltage drops by 20%.

In order to get the same wattage (power) at the sub panel 100 feet away, you have to increase the amps by 20% (to balance out the 20% drop in voltage). That, of course, means that you are dealing with more current (more amperes) and you have to choose a bigger-sized wire. Example: 50 amp wire is usually the 6 AWG (we require at least 62.5A and 6 AWG can handle 65A). If you have to power an electric device 100 feet away, you need 20% amps more. Instead of 62.5A, you’re looking at 62.5A × 1.2 = 75A. In this case, the 6 AWG gauge wire with 65A will not be enough. We need at least 75A. The next wire size that can handle more than 75A is the 4 AWG gauge wire. This one can handle at 85A and is usually used as a 50 amp wire size for 100 feet away sub panels.

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There are quite a lot of questions regarding 50 amp and different voltages. Let’s tackle this one as well:

What Size Wire Do I Need For 50 Amp At 110-240V?

A common misconception regarding 50 amp wire is that we need different wire sizes for different voltages. We don’t need a bigger (or smaller) wire size for 50 amp at 240V than for 50 amp at 110V, for example. In all cases (with the exception when we have to account for voltage loss) we use 6 AWG wire for 50 amps. Now, the wire size and the amps might be the same. With different voltages, we don’t get different amps; we get different power (wattage).

What gauge wire for 50 amp 220V?

For example, a 50 amp wire on a 220-volt circuit (you will need a 6 AWG wire) can handle up to 11,000W of power (this is a very common electricity setting for RVs). Here is how you can calculate that:

Wattage = Amps × Volts = 50A × 220V = 11,000W

If you have a 110V circuit, the 50 amps will produce 5,500W of power. We hope the topic of 50 amp wire sizes is a bit more clear now. You can also check out a similar post for:

learnmetrics.com - 50 Amp Wire Size Details: Gauge, Breaker, 220/240V Example