Are Toilet Seats Universal? How to Replace a Standard Seat

are toilet seats standard sizes

There are so many options when it comes to buying toilet seats that you might want to just buy the first one you see and get out of there.  But, I think I can save you some time and hassle. The first thing you really need to know, is the answer to this question: Are toilet seats universal sizes?

There are two standard sizes of toilet seats in the United States. They are elongated and round. Elongated toilet seats are 18.5 inches long and round toilet seats are 16.5 inches long. To find out what kind of toilet seat you need, measure from the end of the bowl to the middle of the seat post holes

If this all sounds like jargon, don’t worry. In the next couple of sections, I’ll show you the differences between the two, and how you can properly measure the size you need for your toilet seat. 

Are Toilet Seats Universal?

Are toilet seats universal

Just like toilet tanks, not all toilet seats are universal, there are a couple of overall toilet standards that you should know. 

First, the distance between the two bolts that hold your toilet seat to your toilet bowl is standard across nearly all toilets, regardless of what kind of shape it has. These are called seat post holes and they should be about 5.5 inches apart from the center of one hole to the other. 

Second, the width of the toilet bowl is usually the same regardless of shape as well. If the width does vary, it’s usually only by less than half an inch. 

Now that we’ve got those things covered, let’s dig into the different types of toilet seats. 

Elongated Toilet Seat

Elongated toilet seats measure about 18 inches long and about 14 inches wide. 

Elongated toilet seats are preferred by many, especially men, because of their extended size. Because of its popularity, this is the seat that is standard in most large businesses such as hotels, gas stations, and airports.

Plumbing Supply has a great visual chart that shows all the standard measurements for an elongated toilet seat.

Although they’re more common in large businesses, you can also find them in houses and apartments. 

Round Toilet Seats

First off, the measurements. Round toilet seats measure about 16 inches long and about 14 inches wide.

Here’s a visual representation of the standard dimensions of a round toilet seat courtesy of Plumbing Supply.

In general, round toilet seats are more common in homes and houses. They are also used more often in smaller bathrooms because they take up less space than their elongated counterparts.

Also, because round toilet seats are a couple of inches smaller than elongated seats, they tend to be on the cheaper side, but not by much. 

How to Measure Your Toilet Seat

how do i measure my toilet seat

Now that you know about the standard sizes, you probably want to know how to figure out what type of toilet seat you have. 

You need to make sure you get accurate measurements of three things before you go to the hardware store. Those three things are: 

  1. Length
  2. Width
  3. Distance between seat post holes 

Let’s get to it.

1. Length

This is by far the most important measurement. The other two are usually standard so if you don’t want to hassle with remembering three different numbers, just get this one. 

But, I’d advise you to measure the other two just to make sure you have a standard-sized seat.

To get this measurement, measure from in between the seat post holes to the end of your bowl. Make sure you measure to the outside edge of your toilet bowl, otherwise, you’ll end up getting a shorter measurement than you need. 

Here’s a picture for all you visual learners out there. 

Measuring toilet seat length

This will determine if you have an elongated bowl or a round bowl. Just to review, elongated bowls will be around 18.5 inches, like the one I’m measuring in the photo above, and round bowls will be about 16.5 inches. 

2. Width

As I said earlier, the width is usually standard, but just to make sure you don’t have a really weird-sized toilet, take this measurement anyway. 

To get this measurement, just measure across the widest part of your toilet bowl. Again, make sure you’re measuring from outside edge to outside edge. Here’s another picture to illustrate. 

Measuring toilet seat width

If you do get a measurement that’s different than the typical 14 inches, then you may have a non-standard toilet seat which I talk about in the next section. 

3. Seat Post Holes

Lastly, you’ll want to measure your seat post holes to ensure your toilet is a standard size

For this measurement, get out your handy dandy tape measure and measure from the center of one seat post hole to the center of the other. 

If you don’t have your toilet seat off, don’t worry, just try to line up your measuring tool to the center as best you can. Here’s a picture to show you what I mean, I didn’t take my seat off. 

How to measure seat post holes

Your seat post holes should measure 5.5 inches, and, if they do, all standard toilet seats will fit your seat post holes regardless of shape. 

Non-Standard Toilet Seats

european toilet seats

So, you’ve gone through all the steps and measured your toilet seat only to find out that it’s not a standard size. Now what? 

Not to worry, you can still replace your toilet seat if you need to. It just might be a little harder to find the right seat. But first, let’s figure out what a non-standard toilet seat is and why you might have one.

What Is a Non-Standard Toilet Seat?

A non-standard toilet is anything apart from the standard sizes listed earlier in this article. Surprising, I know.

They could be an odd shape, or length, or have seat post holes that are farther apart or closer together than the standard 5.5 inches. 

If you have different-sized seat post holes, you can get replacement hinges for a toilet seat which will match the different sizes of the seat post holes. This also might be cheaper than buying a special toilet seat. 

However, buying new hinges won’t fix every situation. Sometimes, you’ll have to buy a specially-made toilet seat. The kind of seat depends on who the manufacturer is for your toilet.

Proprietary or OEM Seats

You’re probably wondering, ‘Why are there toilet seats that aren’t the standard size?’ 

Manufacturers are constantly trying out new styles and designs in order to stay competitive and innovative. So, they sell small amounts of these new styles and shapes of toilets to see if they have potential in the market. 

These types of seats have two names. They are either called proprietary seats or Original Equipment Manufacturer (OEM) seats. 

In either case, replacements for this type of seat can often be hard to find and expensive to replace. 

But, not all hope is lost, a lot of specialized plumbing stores and DIY stores sell odd-shaped toilet seats at a cheaper price than buying them straight from the manufacturer. 

How To Know What Type of Seat To Get

If you have a non-standard-sized toilet seat and you need a replacement, you first need to figure out the manufacturer of your toilet.

Most toilets have a logo or the name of the manufacturer in between the seat post holes. If your toilet doesn’t have that, take off your toilet tank lid and check for a manufacturer’s label. This will be more common if you have a proprietary or OEM toilet. 

If all you can find is the logo in between the seat posts, that’s alright. Take measurements of your toilet and do one of two things. You can search online for places that sell your sized seat, or you can take it to your local hardware store and see if they can help you out. 

If you find a manufacturer’s label under your toilet tank lid, you should be able to search the manufacturer’s website for replacement parts. 

If you want the cheaper option, check the manufacturer’s website to get the name of your specialized toilet. Then search specialized plumbing stores to find an alternative. Putting it into a search engine should give you lots of options. 

European Toilet Seats/D-Shaped Toilet Seats

Another possibility, if you have a non-standard seat, is that you have a European toilet seat. 

European seats have two styles similar to elongated and round seats, but they also have a D-shaped seat that is pretty common. 

Luckily, you can pretty easily buy this D-shaped toilet seat online and have it shipped to you. Make sure you measure thoroughly before you make a purchase to ensure you’re getting the size you need. 

How to Replace A Toilet Seat

Now that you’ve followed all the steps and have your new toilet seat in hand, you need to replace your old seat with your new seat. 

1. Remove the Old Seat

You need to remove your old seat. To remove your old seat, you need to remove the seat bolts. 

The seat posts are usually attached by a nut and bolt at the back of the toilet seat. Most toilet seat screws are hidden under a little flap on the back. 

To access them, just flip up the plastic flaps with either a fingernail or a flathead screwdriver. 

Now that you can see the bolt, you’ll unscrew it. You will need an adjustable wrench to unscrew the nut underneath the toilet. If you’re trying to unscrew the nut but the bolt keeps spinning, use a screwdriver at the top of the bolt to hold it in place while you unscrew the nut. 

Now for step two.

2. Unpackage the New Toilet Seat

Before you can install the new seat you need to unpackage it. 

The most important thing to remember when you do this is to keep all the pieces together so you don’t lose anything important. 

The new toilet seat may also come with an instruction guide of some kind to help you install your new seat. Set this aside so you can use it in step 3. 

3. Install the New Toilet Seat

Now install your new seat. 

If your seat comes with some instructions, follow those to easily install your new seat. 

But, all you need to do is line up the seat hinge to the holes already in your toilet bowl. 

Then, use the fixings that came with your seat and slide the bolt through the toilet seat hinge and the post holes. 

Screw the nut onto the bolt underneath the toilet bowl. Make sure your bolts are tight or your toilet seat could wobble.

How do you know what size toilet to buy?

To determine the toilet size you need, you first need the rough measurements. This is from the middle of your toilet drain pipe to your wall. If you have limited space, make sure you also measure the width and length of the area that you want your toilet to fit in. 

Are toilet seat hinges universal?

Toilet seat hinges are not universal. There are many different types of toilet seat hinges including standard hinges, soft close hinges, adjustable hinges, and even quick-release hinges. If you want to replace your hinges, check your toilet seat manufacturer to see if your new hinges are compatible with your old toilet seat. 


Leslie has lived in tons of different places that were all in different states of repair. She has experience remodeling and replacing just about everything in a home including the roof. When she's not working on a project, Leslie blogs about home improvement tips to pass on her knowledge to others.

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