In Repair & Maintenance

How to Measure Toilet Rough-In Dimensions Like a Pro

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For some reason, everybody is intimidated by replacing, repairing, or purchasing a toilet. Maybe it’s the thought that this is “real” plumbing work. Maybe it’s the line of about 30 toilets that you’re met with at that home store. One of the most mystical aspects of toilets is the toilet rough-in dimensions. Fortunately, once you understand the concept, it isn’t that difficult to measure for this.

Start with a Good Tape Measure

Here’s the deal: everything in home improvement relies on a good tape measure. You need a tape measure that is easy to read, like this Milwaukee model that has the smaller fractions labeled. Even if you know how to read a tape measure, your eyes tend to go cross-eyed looking at the lines and this prevents that.

You should also consider getting one where the metal tip is magnetic like this one. This magnetic tip will definitely help if you are doing a lot of measuring alone because you don’t always have somebody to hold the end for you.

A 16 foot tape measure is typically plenty and the shorter tape will weigh far less on your toolbelt so you aren’t likely to set it down. Milwaukee makes some high quality tape measures that can withstand being dropped repeatedly (speaking from experience here), bends in the blade constantly, and fast reels. All of this means that you better pick a good one because it will be with you forever.

What are Common Dimensions for Roughing-in a Toilet

  • 10-Inch
  • 12-Inch
  • 14-Inch

There are only a few common dimensions for toilet rough-ins. Of course, if somebody didn’t know what they were doing, they may measure differently. But toilets are made to fit a 10,12, or 14 inch rough in. The most common toilet rough-in dimension by far is a 12” rough-in.

Measuring the Main Flange Rough-In

This is all well and good but how do you measure a toilet rough-in dimension? Essentially, your toilet’s rough-in dimension is a measurement from the wall to the center of the flange, or hole the toilet drains into when it is flushed. If you need to know more about installing a new toilet flange, this Old House has a good video to help you.

What is a 12-Inch Rough-In Size Toilet

12 toilet rough in

Let’s take a 12” toilet rough-in for example. Use the standard process of measuring a toilet rough in. Put the end of the tape measure against the wall that the back of the toilet will be against. Measure to the center of the hole where the toilet drains into when it is flushed. This is your rough-in dimension.

How to Measure Toilet Rough-in Dimensions With a Toilet There

Especially if you only have a single toilet in the home, you may not want to remove the toilet before getting the toilet rough-in dimension. If you measure from the back wall to the toilet bolts, the bolts that hold the toilet to the floor, you will know the rough-in dimensions.

Standard Toilets

A standard toilet is a toilet that sits on the ground and points in a direction perpendicular to the wall it rests against. This is the case for most toilets in the US. If your toilet looks “normal” you have a standard toilet. You measure a standard toilet by measuring from the back wall to the center of the flange as described above.

Corner Toilets

Sometimes a smaller bathroom may have a corner toilet in order to save space. Corner toilets sit at a 45° angle to the walls on either side. To measure the toilet rough-in dimensions for a corner toilet, measure from one side wall to the center of the flange. 

Then measure from the other side wall to the center of the flange. Where the two lines intersect (hopefully in the center of the flange for both lines) is the measurement of the rough-in on a corner toilet.

For example, if you were putting in a 12” corner toilet, measure from the corner down one wall 12” and draw a line at a 90° angle to the wall. Then, measure from the corner down the other wall 12” and draw a line at a 90° angle to the wall. Where the two lines intersect should be the center of the pipe the toilet drains into when you do the plumbing.

Wall Mount Toilets

wall mount toilet rough-in dimensions

Many people would think that a wall mount toilet would be very different than a standard toilet when you measure rough-in dimensions. Actually, it’s exactly the same but turned on its side. Instead of measuring along the floor, you measure along the wall.

So, to measure the rough-in for a wall toilet, measure from the floor directly underneath the flange to the center of the flange. That distance is your toilet rough-in dimension. It really is exactly the same to measure a wall toilet as it is to measure a floor mounted toilet.

Toilet Rough in Adapter

For some people, they have a “non-standard” toilet rough-in dimension in their house. If you absolutely have to, you can get a rough-in adapter to make a smaller toilet fit a larger rough-in dimension.

However, these adapters do not have a good track record, as of the writing of this article, and they are not a recommended solution. It is worth it to get a toilet that has the rough-in dimension that matches your existing rough-in.

Other Important Toilet Dimensions

common toilet dimensions to know

When you are preparing to go to the hardware store for a new toilet, you need to know a few other crucial dimensions as well. Just to make sure you get the perfect toilet, make sure that you go to the store with all of these dimensions as well.

How Far from the Sidewall Should a Toilet Rough-in Be

When you are preparing a new toilet rough-in, make sure that the center of the toilet flange is at least 15” from the closest sidewall or other side obstruction. This means that the toilet should be 15” from any nearby vanities as well. Not only will users be more comfortable this way but is also gives you plenty of room to install it.

Distance from Toilet Front to Obstruction

The front of the toilet should be no closer than 24” from the closest obstruction to the front. Any wall or obstruction closer than 24” will make a user sitting on the toilet feel like they don’t have enough room for their knees or to maneuver.

Placing the Supply Line

Another distance that has a “normal” measurement is the distance the supply line is from the floor. The supply line is typically at least 7” above the finished floor. This gives you enough room to put most trim pieces you may choose and it still gives you enough room for the escutcheon around the supply line to make it look nice.

Bowl Height

ada toilet bowl height

Bowl height is something that you can decide for yourself because there is no standard dimension. Taller bowls are easier to get up from so they may be labeled as an “ADA height toilet” since they are easier for the older population. However, if you are prone to constipation or hemorrhoids, you will find a lower bowl height easier to use without inflaming those issues.

Tank Height

There are different tank heights that you need to accommodate, especially if you already have an over-the-toilet shelf unit to fit under. Make sure to measure how far from the floor to the nearest vertical obstacle you have to work with. If you buy a toilet with a tank too tall for your space, you won’t be able to install it.


Measuring for a new toilet or a replacement toilet is actually not that difficult. It follows the basic principles of measuring for home improvement. Measure every possible dimension you can imagine, then measure more, and then take some pictures just in case. But just remember, when you’re measuring toilet rough-in dimensions, that it’s easier than you think.