There’s no official rule regarding how many outlets can be on a 20 amp circuit. And there’s no official rule about how many outlets can be on a 15 amp circuit either. But there are guidelines you can and should follow to avoid unnecessary breaker trips. And there’s another rule that’s much more important than the number of outlets.
The National Electric Code has no rules regarding how many outlets you can daisy chain off a single breaker. But generally speaking, it’s best to keep the number below 13 because of average current draw.
How many outlets can be on a 20 amp circuit
While there is no legal limit to how many outlets you can put on a 20 amp circuit, you can estimate how many would be a good idea. Just like I tell my kids, if you wonder if something is illegal, that’s a sign it may not be the best idea, so stop and think before you do it.
So let’s look at what the math says. Don’t worry, it’s junior-high math.
On average, we tend to plug 1.5 amps worth of draw into each outlet. Nothing stops us from plugging in more, but that’s good enough for estimation purposes.
When you divide 20 by 1.5, you get 13.33. Of course you round that down to 13. So if you want to avoid problems, keep the number below 13.
Now there’s a school of thought that says to keep it even lower than that. You’re not supposed to run your circuits at more than 80 percent capacity. So some people say to go to 80 percent of 13, which would be 10 outlets.
The counter argument is you’re not going to plug a consistent 80% draw into every outlet. The counter-counter argument is that following the 80 percent rule anyway gives you headway, to accommodate those people who buy above-average everything.
At any rate, the rule is if you like to push limits, go with 13. If you like to play it safe, go with 10.
The limiting factor here is the wire. On a 20 amp circuit, you need the yellow wire, which is 12-gauge wire. If you use the cheaper white wire and overload it, you can burn that wire before the breaker trips. That’s the rule you need to be careful to follow.
How many outlets can be on a 15 amp circuit
There’s also no legal limit to how many outlets you can put on a 15 amp circuit. But the same math tells us how many would be a good or bad idea.
The same 1.5 amp rule applies here. It doesn’t take a math genius to see when you divide 15 by 1.5, you get 10. So to avoid problems, keep the number at or below 10.
The 80 percent rule says to lower it to 8.
So, the rule is if you like to push limits, go with 9 or 10. If you like to play it safe or like over-engineered solutions, go with 8. If you’re the type who uses yellow-sheathed cable on 15-amp circuits, 8 is the number you want.
Why the National Electric Code is silent on this issue
There’s a reason why the National Electric Code doesn’t put a limit on the number of outlets on a circuit. The breaker protects you. If you plug too much stuff in, the breaker will trip. And in theory, you can overload a breaker with a single outlet, and stay under capacity even if you plug 50 outlets’ worth of stuff into it. It all depends what you’re plugging in, which is a nearly infinite combination of possibilities.
As long as the breaker is working and you use the right wire–white-sheathed electrical cable is fine for 15 amps, but you need the more expensive yellow-sheathed cable for 20–the number of outlets you chain off the breaker isn’t a major problem. The system will protect you if you try to push the limit.
You won’t burn your house down if you put more than 13 outlets on a single breaker. But if you don’t want to be constantly blowing breakers like in the movie A Christmas Story, following these guidelines is a good for your quality of life, at least.
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.
The white vs yellow color coding is a thing now but it hasn’t always been. If you’re checking out wiring in an existing home, you may need to look at the markings on the wire to see whether it’s 14 gauge (what is now white sheathed) or 12 gauge (what is now yellow).