What Is The Compatible Toilet Size?

Measurements can be a tricky thing for the consumer that wants to manage their own bathroom project.

The problem starts with understanding rough in, and it ends with not accounting for uneven surfaces and other random problems.

What turns out to be the easiest part of installing a toilet turns out to be the most nightmarish if you’re not prepared.

And even then, the most prepared people still fall prey to the nasty surprises that happen when you remove the old toilet and realize some measurements were off.

This guide will go into detail explaining some of the better parts of things to look out for when you are trying to figure out the size for your bathroom.

Hopefully, it will dispel most of your fears, and give you something to look forward to rather than something to fear.

One Piece VS Two Pieces

This is an argument that has been brought up before but should be touched on again. When considering buying a toilet you should always lean towards choosing a one piece toilet first and then go look at the two-piece options after exhausting your one-piece choices.

This is because you automatically gain a couple of extra inches by getting the 1 piece model, and those few inches can make a world of difference in an installation where even half an inch can make all the difference.

You’ll also gain extra space with this choice which will help with installing extra things like a toilet seat bidet or a sink. You can’t really account for every inch of space lost with extra pieces, so having a bit of an edge with a 1 piece toilet really helps.

Tankless Models Are Awesome

If you want to maximize the amount of space, then going for the best selling tankless toilet in the industry is not only a smart idea but one that will open up customization options to the max.

Tankless models are great because they take the best part of a toilet and combine it into a smaller model that just contains the seat. The setup and installation are a little different but easy enough to where the common user will love the benefits and ease of use.

If your priority is saving bathroom space, then this is the smallest toilet you can get and a great toilet for small spaces.

They are available in both round and elongated seat sizes, and give you everything that you would expect out of a luxury toilet while also offering the best size advantage. 

A big benefit of these toilets is that they can also go wherever there is an outlet or access to plumbing.

This means virtually anywhere in your house that you would have it, so tankless models basically have zero size concerns since they can go wherever they please.

This is a big advantage over their bigger brothers with the tanks and makes it the superior option for the customer that doesn’t want to use up a lot of space in the bathroom.

Rough In Size

The most important measurement to know, the rough in size is the measurement from the wall behind the toilet to the closet bolt of the toilet.

The usual amount of inches is usually 10-12 but can be as high as 14. Here you can read more about toilets with 10-inch rough-in.

Getting this correct is vital! And this is another reason why tankless and 1 piece, like the Toto Neorest 550, models are superior to 2 piece toilets.

A bad rough in measurement can at least be made up for a bit by these models, rather than punishing you for a bad take.

Getting a smaller toilet will fit just fine, but getting a taller toilet could require you to change your plumbing, or in extreme cases move the wall.

Neither one of these is a good option if you just want to install your toilet and get on with your life, so use caution when measuring rough in. And remember that 1 piece toilets and tankless models are superior!

Bowl Height & Seat Type

Although less important than rough in, this still deserves its own section.

Seat type in the market has shown favoritism for the elongated seat, here is our guide to the best elongated toilets, although the round seat is still in the rotation for all brands.

The main reason you would want an elongated seat is that it is universal for all sizes adults and kids, whereas toilets for the elderly would have comfort issues with a round seat.

The bowl height is purely subjective, as even with the bigger brands focusing on ‘chair height’ toilets, you’ll notice that your comfort level is going to be vastly different than the next person’s.


Choosing the right size is going to begin with getting the rough in size correct and then going with a compatible toilet. Think about who is using it the most and it will give you a general idea of what to look for. In the end it will come down to a simple cause and effect to getting that perfect toilet.

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Mr Handyman
Mr Handyman

Hi, My name is Charles. Also known as (Mr. Handyman)
I have been in the home improvement industry for a number of years.

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