Difference Between 10 and 12-Inch Rough-In Toilets

When you are remodeling your bathroom, one of the decisions you will have to make is what type of toilet to install. One option is a 10-inch rough toilet, and another option is a 12-inch rough toilet. So, what is the difference? And which one is suitable for your bathroom? Keep reading to learn more!

Toilet Rough-in means the distance from the wall behind the toilet to the center of the drainpipe.  So, the major difference between 10 and 12-inch rough-in toilets is their difference from the rear wall. A 10-inch rough-in is at a distance of ten inches from the back wall, while the 12-inch rough-in is at a distance of twelve inches from the back wall. Nowadays, 12-inch rough-in toilets are standard.

Further, in this article, we will talk about the pros, and cons of each rough-in type and compare them. Finally, we will explain to you how to measure the rough-in dimensions of the toilet.

10″ Rough-in Toilets

10″ Rough-in Toilet

As you have known, 10″ Rough-in means the center of its flange is ten inches from the back wall. These rough-in dimensions are not common nowadays. However, you may find such toilets in older homes. In addition, these toilets are ideal when the bathroom is to be built in a very small space, like powder rooms.

If you are planning a renovation and your older toilet is a 10″ Rough-in toilet, then you must make sure to buy a new toilet with the same dimensions. However, conversion to 12″ Rough-in is also possible with a special flange (offset) flange. 


  • Can be a good option for small bathrooms.
  • They save space.
  • Convertible 12” rough-in
  • Can easily fit in children


  • Less common size so may be harder to find
  • Available in limited designs.
  • Prone to clogging

12″ Rough-in Toilets

12″ Rough-in Toilets

These are toilets that are spaced twelve inches from the rear wall facing the toilet tank.  12″ Rough-in Toilets are quite common these days. And being common, there are available in different designs and models in the market.



  • Not convertible to 10” rough-in

10 vs 12″ Rough-In Toilets

Now, let’s compare 10 and 12-inch rough-in toilets in terms of their dimensions, flushing, usage, and compatibility.


a red arrow indicating the distance of drain pipe from the wall
Image from Sim Siang Choon Hardware

The major difference between the two toilets, as their name suggests, is their measurement from the rear wall. A rough-in of 10 inches means the toilet drain pipe center is 10 inches away from the back wall. Similarly, rough-in dimension of 12 inches, the toilet drain pipe center is 12 inches away from the back wall.

Flushing Power

In terms of flushing power, 12-inch rough-in toilets are considered much better. They are less prone to clogging and blockage. 


10-inch toilets are ideal for powder rooms since 12-inch toilets won’t fit there. When residing in humid areas, a toilet with a rough-in of 12 inches is recommended. Since a 10-inch rough-in toilet is likely to get wet and grow mold, it can be a disaster to install them in those areas.

To figure out, which kind of toilet is suitable for your bathroom, you need to find out the rough-in dimensions. Let’s see how you can do that.

Measuring the Toilet Rough-in: A Comprehensive Guide

For measuring the rough-in dimension of a toilet, you will need a measuring tape and a marker or a pencil.

Find Rough-In Without an Existing Toilet

If the toilet is not installed, the floor is bare, you just have the drain pipe hole. In that case, measuring the rough-in is quite simple.

  1. Find the drain hole on the floor. Locate its center.
  2. Now, start measuring the distance from the center of the drain hole to the bare wall. If the wall has an extended baseboard, ignore it and take distance from the bare wall.
  3. In case you start measuring from the molding, add its thickness in the final reading.
  4. Now, check if the dimension is near 10 inches or 12 inches. If it isn’t, you probably have measured the length wrongly.

Finding Rough-In for Floor-Mounted Toilets

Rough-In for Floor Mounted Toilets
Figure 1-Rough-In for Floor Mounted Toilets

For an installed standard or floor-mounted toilet, the method for measuring the rough-in is somewhat different. Follow these steps to measure the dimensions accurately.

  1. Determine the exact location of the toilet’s floor bolts. Examine the underneath of your toilet for any bolts or covers. You can use tape to mark the spots of the bolts.
  2. Measure from the floor, over the toilet’s base bolts, and back to the wall. The resulting measurement is the “rough-in” for the toilet.
  3. Don’t take measurements along moldings. If your wall has a baseboard, move the starting point of your measuring tape up to where the wall is completely bare. If necessary, measure the baseboard’s width and add that number to your overall measurement for precision.
  4. Verify your answers. If your measurement isn’t a multiple of 10, or 12, you should probably check it again.

You must be careful not to waste money by getting the incorrect rough-in toilet.

Finding Rough-In for Corner Toilets

Rough In for Corner Toilets
Figure 2-Rough-In for Corner Toilets

If the toilet is to be installed at the corner. Then, to determine the rough-in dimension of a corner toilet, you need to measure the perpendicular distance from the center of the drain pipe/bolts to any side of the wall.

  1. Locate the bolts and find the flange underneath the toilet. The toilet flange (drainpipe) is hidden by the current toilet, so you will have to estimate its placement using the bolts you just found. The flange for the toilet should be set halfway between the two bolts.
  2. Make a note of where the flange of your toilet is located. Mark the middle of the toilet flange with tape for simple measurement.
  3. From the middle of the toilet flange, measure the distance to the walls on either side, as shown in figure 2. 
  4. You don’t have to measure the distance to the corner where the walls meet. Instead, you have to measure the perpendicular distance to each side wall. You can use measuring squares for precise measurements.

Finding Rough-In for Wall-Mounted Toilets

Rough-In for Rear Outlet Toilets
Figure 3-Rough-In for Rear Outlet Toilets

The rear-outlet or wall-mounted toilets are the ones with a drain on the side instead of at the bottom. In this case, measure the distance from the bare floor to the center of the drain. This will give you its rough-in dimension. 

Can you replace 10-inch Rough-in Toilet with 12-inch Rough-in?

A benefit of using 10-inch rough-in is that it may be upgraded to 12-inch rough-in, despite its dated appearance. This is accomplished by installing an offset flange between the toilet’s flush output and the main drainpipe. A toilet flange functions as an adapter for rough-in plumbing, allowing for the smooth transition from one installation to the next while protecting the piping from any harm.

Final Words

There you have it, the difference between a toilet’s rough-in dimensions. Be sure to take careful measurements before making any decisions. And, as always, if in doubt seek professional help. A few extra dollars spent now could save you a fortune down the road. Thanks for reading!

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