How to Know if Your Toilet Seat is Round or Elongated

To replace a toilet seat, you must first know the type and size of toilet you already have. This is easy for plumbers who don’t even have to measure anything but a homeowner will need to measure to be sure.

Toilet seats are either round or elongated in the United States.  You can however find other shapes like square or D-shaped toilets seats but those are more common in Europe.


Round toilet seats as their name imply have a round or circular front. Elongated toilet seats on the other hand are oval shaped.

To know if you have a round or elongated toilet seat, remove your toilet seat and measure the distance between the center of the toilet seat mounting holes and the front edge of the bowl. If you get 16.5 inches you have a round toilet seat but if you get about 18.5 inches you have an elongated toilet seat.

As you can see from the above statement, you need to measure the toilet bowl and not the actual toilet seat. Measuring the seat (especially the lid) will give you a wrong figure since some toilet seats are telescopic in design.

You cannot replace a round toilet seat with an elongated toilet seat. A round toilet seat should be replaced with a round toilet seat and the same for elongated toilet seats. You can however replace a round toilet with an elongated toilet.

The width of a toilet seat is not that important. You just need to get the length right. Toilets in the United States also have a standard length between the toilet seat mounting holes of 5.5 inches.

The main advantage of elongated toilet seats and bowls is that they offer more space to sit on and are therefore more comfortable to use than round toilet seat and bowls. Round toilets are however space-efficient and are best for people with small bathrooms.

To read more on the pros and cons of elongated toilets versus round toilets check out this post.

How to Measure a Toilet Seat Dimensions

In most cases, you don’t even need to measure if you have a round or elongated toilet seat. The shape of the seat and /or toilet bowl will tell you which shape of toilet seat you need to buy.

If you however need to be absolutely sure, measuring does make sense. This is how to measure for a toilet seat:

1. Remove the Toilet Seat

As I have mentioned, you need to measure the length of the toilet bowl between the center of the 2 seat-mounting holes and the front edge of the bowl. 

It is hard to do that with the seat still installed. This is why I recommend removing the toilet seat first. And now this is how to remove a toilet seat:

  • Pry off the toilet seat bolt covers. Toilet seats are installed using 2 bolts. The bolts are tightened using nuts from underneath the bowl while their heads are covered using plastic tabs. Pry off the tabs using a flathead screwdriver.
  • Use a Philips screwdriver to turn the toilet seat bolts counterclockwise to loosen them. As you are likely to find out, the bolt will start spinning instead of loosening. In that case what you should do is back off the nut underneath the bowl using a wrench.
  • If you have metallic bolts which are corroded and won’t come off, consider spraying then with a penetrating oil and wait for about 15 minutes. If they will still not come off, cut the bolts using a hacksaw blade.
  • With the bolts out, you will only need to lift off the seat.

2. Measure the Length of the Toilet Bowl

  • Place your measuring tape at the center of the 2 seat mounting holes on the bowl and measure the length of the bowl all the to the front edge of the bowl.
  • Try to keep the measuring tape as central as possible to get an accurate figure.

Round Toilet Seat Dimensions


If you get a reading of 16.5 inches, you have a round toilet seats and you will need to buy a similar one to replace it with. Since toilets and toilet seats have small differences in size and also accounting for your accuracy, you are likely to get between 16 and 17.5 inches for a round toilet seat.

Elongated Toilet Seat Dimensions


Elongated toilets are usually about 18.5 inches in length. If you measure and get between 18 and 19.5 inches then you have an elongated toilet seat.

Can You Use an Elongated Toilet Seat on a Round Toilet?

You absolutely cannot replace a round toilet seat with an elongated toilet seat. Elongated toilet seats are about 2 inches longer than round toilet seats which also mean they protrude 2 inches from the edge of the round toilet bowl.

Even if you manage to install an elongated toilet seat on a round toilet bowl, it will not be comfortable and you will break it on the first day.

Remember that the elongated toilet bowl is oval-shaped just like the elongated seat while round toilets are circular. This means that a big part of the toilet seat will not be supported. The moment you sit on it you will ether fall off or it will snap.

What you can do is replace a round toilet with an elongated toilet and vice versa. That is an expensive upgrade however and you will need to be financially read for it.

If you have a round, old and slow/weak flushing toilet and you have enough space in your bathroom, you should definitely consider installing an elongated toilet. Make sure that you check the rough-in as well.

Pros and Cons


The following are the advantages/pros of elongated toilet seats:

  • Very comfortable
  • Modern look
  • Available in different styles and designs


  • More expensive
  • Less comfortable for kids
  • Needs more space

The following are the pros of round toilet seats:

  • Relatively cheaper
  • Comfortable for kids
  • Space-efficient


  • Not comfortable for adults
  • Few options to choose from
  • Old design

Considerations when Buying a Toilet Seat

Apart from the shape of the toilet seat, there are other things that you also need to consider when buying a toilet seat.

The first thing is material. Toilet seats are either plastic or wooden. Wooden toilet seats are stylish, warmer, but they scratch and/or break easily. Plastic toilet seats don’t break that easy but are relatively colder to sit on.

You also need to consider seats with a quick-release/install mechanism. These seats are easy to remove which makes cleaning the toilet bowl very fast and easy.

Bidet toilet seats are another thing to consider. They are more expensive than regular toilet seats but definitely more comfortable to use.

Toilet seats can also be heated, which often comes with the nightlight feature as well. If you live in a cold area you should definitely consider this option.

Finally, you may want to buy a slow/soft close toilet seat especially if you are disgusted by the slamming sounds of a toilet seat. These seats close slowly, which means they make no noise and will also not pinch a child’s fingers.

If you need to read a review of some of the best toilet seats, check out this post.

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