* What is Toilet ROUGH-IN & How to Measure?

What Is Toilet Rough-In and How to Measure It?Are you considering replacing your toilet or choosing one for your new home?

If so, things such as the bowl’s shape, toilet’s height and whether the toilet is one or two-piece will be just some of the items on your list of decisions to make.

Before getting to any of those, however, you will have to consider the single most important measure of a toilet, the toilet rough-in.

What is toilet rough-in and why is it so important?

Simply said, toilet rough-in is a measure that determines the position of a toilet waste output relative to the wall or floor of your bathroom.

In most cases, it is the distance between the wall and the middle of the closet bolts, the bolts sticking out of your floor that are used to hold the toilet bowl in place.

But, more about that in the next section about measuring toilet rough-in.

Now that you understand what the term means, you can also see why it’s the most important factor to consider when choosing a toilet to buy.

Unless you want to redo your plumbing completely (which, trust me, you do not want to do in most cases), you will have to choose from toilets that have the same rough-in as your bathroom was built for, or the bowl will not fit at all or will fit badly causing a lot of issues.

In other words, toilet rough-in is the one factor which you cannot be flexible about when choosing your new toilet bowl.

How to measure toilet rough-in?

When measuring the rough-in of your toilet, you will first have to determine which of the following toilet types you have:

  • Standard toilet with the waste outlet going into the floor
  • Corner toilet with the waste outlet going into the floor
  • Rear outlet toilet with the waste coming out of its back.

Most likely, you will have a standard toilet in which case you will have to measure the distance between the wall and the middle of the closet bolts as mentioned in the previous section.

In case you have four closet bolts rather than the typical two, you have to measure the distance to the pair of bolts closer to the wall.

In case you have a corner toilet, the rough-in is still the distance between the wall and the bolts. But, in this case, the distance should be equal from either of the two walls that form the corner in which you will be placing the toilet.

Finally, if your toilet waste output is in the wall rather than the floor, the toilet rough-in is the distance between its center and the floor.

The one thing to keep in mind regardless of the type of toilet you have is that when taking the measure, you will have to start at the “top layer” of the wall or floor.

And so, if you plan to replace your tiles or put new tiles on top of your existing ones, you will have to take that additional layer into account.

What are standard rough-in sizes?

The above might make it seem like it is really easy to pick a toilet that will not fit your bathroom.

Luckily, though, most of bathrooms use standard toilets and have waste outlet in the floor with one of the following three rough-in sizes:

  • 12-inches: Nowadays, this is by far the most common of the three. That also means that if this is the measurement you get then you will have the biggest selection of toilet bowls to choose from.
  • 10-inches: This is the second most common of the three sizes since it is still used even in the present, especially in case of smaller bathrooms. However, it was more widely used in the past.
  • 14-inches: This is the least common of the standard sizes. It was widely used in the past, though, and so depending on the age of your house, you might still find yourself in this category. Unfortunately, the fact that this is the least used size also means the toilet bowls you will be able to choose from will be fairly limited.

To measure your toilet’s rough-in, you can, of course, use a tape measure.

But, in case you have a standard toilet and don’t have a tape measure handy, the easiest way to do so is by using a piece of letter-size paper.

Since the paper’s longer side is 11 inches and its diagonal is 13.9 inches, it makes it really easy to figure out which of the three standard sizes you have in your bathroom.

Can you get a toilet with different rough-in than your plumbing is built for?

When measuring your toilet rough-in, chances are you will not get a nice round number perfectly fitting one of the three standard sizes. However, you will very likely get a number very close to it.

In that case, do not worry about it too much.

Just remember that you have to get a toilet built for a shorter rough-in than your actual measurement or otherwise it will not fit. And so, if your tape measure will read 12 and a half inches, you will have to get the 12-inch toilet.

With that in mind, in theory, you could even get a 10-inch toilet in the above situation.

However, you should not do that as there will be a large gap between the back of the toilet and the wall which will not only look bad, but will also be impractical as anything you place on top of the toilet’s tank will easily fall behind it.


As you can see above, getting the rough-in correct when choosing a toilet is important both for practical and aesthetic purposes.

To get the number, in most cases, you will have to measure the distance between the wall of your bathroom that the toilet will be placed against and the bolts that are sticking out of the ground to hold the toilet in.

And, in most cases, you will get a number close to one of the three standard measures: 10-inch, 12-inch, and 14-inch.

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