* Are Toilet Seats Universal? (& How to Measure Them)

If you are renovating a bathroom or building a new one, something that you will probably need is a toilet. However, maybe the old toilet is still fine, and it just needs a bit of a touch-up, such as a new seat. So, if you need to replace a toilet seat, how do you know which one to get?

Let’s figure out how to choose the toilet seat right now, at least in terms of the size.

Are Toilet Seats Universal? (& How to Measure Them)

Are Toilet Seats Universal?

The simple answer here is that no, toilet seats are not universal, as there are two main types, and which type you get will depend on the toilet bowl. While very many toilet seats are interchangeable from one toilet to another, this dichotomy between the two types of toilet seats out there does create a bit of a problem.

You have rounded toilets and elongated toilets. As you can probably tell by the name, rounded toilets feature almost perfectly round bowls and seats. On the other hand, elongated toilets are more oval in shape, or in other words, are a bit longer than they are wide. Simply put, no, a rounded toilet seat will not fit on an elongated toilet, and vice versa.

Toilet Seat Now, with that being said, if we are talking about the universality of elongated toilet seats or rounded toilet seats, then yes, you could say that they are universal. Generally speaking, one rounded toilet seat should fit on most rounded toilets, and the same can be said for elongated toilet seats. Both rounded and elongated toilet seats have standard sizes, so if you have a standard elongated toilet, it should fit all standard elongated toilet seats.

So, the bottom line is that elongated toilet seats are (usually) universal for elongated toilets, and rounded toilet seats are universal as far as (virtually all) rounded toilets go. However, across the board, if we are talking about all toilet and seat types, then no, they are not universal.

What are the Standard (and Non-Standard) Sizes of Toilet Seats?

OK, so what we do need to say here is that the title of this article is a bit confusing, but this is because this is a question that many people ask (size of toilet seat). However, as toilet professionals will tell you, technically speaking, toilet seats do not come in sizes.

Toilet seats come in two types, as discussed above, elongated and rounded. The issue that we have with the semantics here is that these two different types of toilet seats are different sizes (from each other), but both of them only have one standard size, so it can be a bit confusing in terms of the terminology.

Our question is if all elongated toilet seats are the same size, then can you really say that there are different sizes at all? Semantics aside, let’s figure out how big toilet seats are.

The Three Important Dimensions

When it comes down to it, there are three important dimensions that you need to be aware of. This includes the width and length of the seat, as well as the spacing between the toilet seat post holes.

1. Seat Post Holes

What can be said is that all toilets, at least in the US, feature seat post holes that are 5-1/2 inches apart. So, in this sense, this is a standard universal size of seat post holes for all toilets, both elongated and rounded.

2. Length

The major difference between the different types is that from front to back, elongated toilet seats are 18-1/2 inches from the posts to the front of the rim, whereas rounded toilet seats are 16-1/2 inches from the posts to the front of the rim. So, we suppose that you could say that these are the two standard sizes.

3. Width

We have figured out that both round toilet seats and elongated toilet seats have seat post holes placed 5-1/2 inches apart. Moreover, we have also figured out that the standard length of a rounded toilet is 16-1/2 inches, whereas the standard length of an elongated toilet is 18-1/2 inches. Unless you get something custom or super unique, this is always going to be the case.

In terms of the width, all standard toilet seats, both elongated and rounded, are 14 inches.

So, as you can tell, the only real difference between any and all toilet seats is their length. Generally speaking, all elongated and round toilet seats are the same width and have the same spacing between the seat post holes.

A Note on Non-Standard Toilet Seat Sizes

Square Toilet Seat Asking what the sizes of non-standard toilet seats are, is a very funny question if you think about it. It is impossible for us to create a list of non-standard toilet seat sizes just because of the fact that they are non-standard. There is no set list. Technically speaking, a non-standard toilet seat can take any size or shape. We can’t tell you how large these are just because they are non-standard. The sizes could be totally random, as someone could custom-build their own toilet to any size they see fit.

However, what we can say is that generally speaking, toilet seats will only differ by a couple of inches (the non-standard ones). For instance, if an elongated toilet seat is 18-1/2 inches long, then a non-standard elongated toilet seat might be as short as 16 inches or as long as 20 inches, but generally no more or less.

On that note, you may also find square toilet seats or ones that have odd shapes. However, as far as toilets that you can buy in normal stores go, you will be stuck with either rounded or elongated ones.

How to Measure a Toilet Seat

The only thing really left to do today is to figure out how to measure your toilet seat. Based on the information we have provided you with above, it is very easy to do. There are only three short steps that you need to know to measure your toilet seat:

  • First, measure the space in between the seat post holes. Once again this should be 5-1/2 inches for a standard toilet.
  • Next, measure from the seat post holes to the front of the toilet bowl. If you get 18-1/2 inches, you have an elongated toilet. If you get 16-1/2 inches, you have a rounded toilet. If you get neither of those, then you have a non-standard toilet.
  • The only thing left to do is to measure the width of the toilet bowl. Measure the widest part at the top of the bowl. If you don’t get 14 inches, you have a non-standard toilet.


There you have it folks, everything you need to know about measuring toilet seats and the universality of the seats across the two standard toilet types. Also, keep in mind that there are different types of toilet seats based on the material they’re made out of and other factors.