Toilet Rough-In | What is It? How Do You Measure It?

Last Updated on July 28, 2023 by toilethaven

When buying a new toilet, the rough-in measurement is the first thing you must consider before actually buying the toilet. Otherwise, you will be stuck with a toilet you cannot install.

The rough-in of a toilet is the distance between the toilet’s rear finished wall and the center of the drain line. You can as well measure from the wall to one of the mounting bolts. Toilets have a standard rough-in of 12 inches, although some have a 10 or 14-inch rough-in.

You must always make sure that you measure a toilet’s rough-in from the finished wall and not the baseboard or stud wall. Measuring from the baseboard or stud wall will give you an error of half an inch.

To know if your toilet has a 10, 12, or 14-inch rough-in, measure the distance between the toilet’s rear finished wall and one of the mounting bolts. Alternatively, use the toilet’s model number (found inside the tank) to search for its specification sheet online, where you will find its rough-in

Toilet Plumbing Rough-in Diagram

You can replace a toilet with a rough-in of 10 inches with a toilet with a rough-in of 12 inches, although a 2-inch gap will be left between the tank and the wall. The opposite is, however, impossible. It is also possible to replace a 12-inch rough-in toilet with a 14-inch rough-in toilet but not vice versa.

The rough-in of corner toilets and rear discharge toilets is however measured differently from that of standard toilets.

It is very important to make sure that you measure the rough-in of your toilet if you are planning to replace your old toilet with a new one. If you are looking for a good toilet, I have reviewed some of the best ones in this post.

To measure the rough-in of a toilet without removing the toilet, grab a measuring tape and measure the distance between the toilet’s rear finished wall and one of the mounting bolts. Alternatively, look for its specification sheet online using its model number.

The best way to know the rough-in of a toilet is to look for its model number inside the tank and then use it to search for the specification sheet from the manufacturer’s website. Apart from the rough-in measurement, you will also be able to see all the other toilet dimensions.

How to Measure the Rough-in of a Standard Toilet

While talking about toilet rough-in, a standard toilet is one which is installed against the bathroom wall and has a floor outlet. These are the most common types of toilets.

In this case, you will need to measure the distance between the toilet’s rear finished wall and the center of the drainpipe. It is important that I emphasize that you need to measure the distance from the finished wall.

If you are taking the measurement from a stud wall, most often, a ½ inch drywall will be installed. Expect, therefore, to have an error of about half an inch.

So if you get a 12.5-inch rough-in from the stud wall, the correct rough-in will, in essence, be 12 inches. The same also applies to toilets with 10 or 14-inch rough-ins.

It is always important that you also take the measurement from the finished wall and not the baseboard. Doing this can give you an error of up to ½ inch.

If you measure your toilet’s rough-in and get 11.5 inches as the rough-in, there is a chance that you measured from the baseboard and not the wall, and therefore the correct measurement is 12 inches. 9.5 inches will be for a 10-inch rough-in toilet and 13.5 inches for a 14-inch rough-in toilet.

As I have said, you measure the distance from the wall to the center of the toilet’s drainpipe. What if the toilet is already installed?

Measure the distance from the wall to one of the 2 toilet bolts. A toilet is fastened to the floor using 2 bolts, one on each side of the bowl, sometimes covered with plastic caps.

These 2 bolts are Usually hooked on the toilet/closet flange at the 3 and 9 o’clock positions and are, therefore, at the center of the drainpipe.

How to Measure the Rough-in of a Corner Toilet

Corner toilets are compact toilets installed at the corner of a bathroom. They are specially installed in small bathrooms to economize space.

To measure the rough-in of a corner toilet, you will need to measure the distance between the finished wall of either of the 2 adjacent walls and the center of the toilet drainpipe.

Unlike a standard toilet, you cannot measure the rough-in of a corner toilet from the wall to the toilet bolts. When you do that, you will not account for the distance between the bolts and the center of the drainpipe.

It is, therefore, a little harder to measure the rough-in of a corner toilet since you will first need to remove it. Here is how to remove a toilet.

I have written a whole post reviewing some of the best corner toilets in the market. Read it here.

How to Measure the Rough-in of a Rear-Discharge Toilet

Rear discharge toilets, which are also known as back outlet or rear outlet toilets, discharge their waster from their rear and through the bathroom wall instead of the floor.

They are the best toilets for apartment developers since their design allows the developer to stack up more floor units. Their design does not work that well with gravity flushing, and hence most of them are pressure-assisted.

To measure the rough-in of a rear discharge toilet, measure the distance between the finished floor and the center of the toilet’s waste outlet.

I have also written a detailed review of some of the best rear discharge toilets. Read it here.

Toilet Rough-In Adapter

A toilet rough-in adapter is an adapter that is used to convert a 12-inch rough-in toilet to one with either a rough-in of 10 inches or 14 inches. This is because toilets with a rough-in of 10 or 14 inches are harder to find than standard rough-in toilets.

This adapter is mostly used by Toto and is called the Toto Unifit Adapter. The problem with this adapter is that it only works with Toto skirted toilets only.

Two of the best-skirted Toto toilets are the Toto Carlyle II and Toto Vespin II. Toto Carlyle II is the skirted version of the Toto Ultramax II, while Toto Vespin II is the skirted version of the Toto Drake II.

I have compared both of these 2 toilets in more detail in a separate post. Read it here.

Another alternative to a toilet rough-in adapter is to buy an offset toilet flange. An offset toilet flange works the same way as this adapter but works with all toilet types. Read more about offset toilet flanges in this post.

Can You Replace a 14-inch Rough-in Toilet with a 12-inch Rough-in Toilet?

You can replace a toilet with a rough-in of 14 inches with one with a 12-inch rough-in, but a small gap will be left between the toilet tank and the wall. You, however, cannot replace a toilet with a 12-inch rough-in with a 14-inch rough-in toilet.

Think of it like a parking spot. You can park your car where a bus has been parked, but you can’t park a bus in a spot meant for a car.

You can also replace a 12-inch rough-in toilet with one with a rough-in of 10 inches, but a gap will also be left between the tank and the wall. A 10-inch rough-in toilet can only be replaced with one with the same rough-in.

If you don’t mind the idea of a toilet leaving a gap between it and a wall, then you are lucky. For those of us who insist on the real thing, then you have to shop for an exact match.

Best 10-inch Rough-in Toilets

If you have an old toilet with a 10-inch rough-in that you need to replace with a modern toilet of the same rough-in, these are some of the best toilets with a 10-inch rough-in:

1. Toto CST744EF.10NO.01 Eco Drake

• Elongated toilet bowl
• 1.28 gallons per flush
• Two-piece toilet
• ADA height
• Toilet dimensions: 28.8 x 16.5 x 29.4 inches

2. Kohler K-3889-0 Highline Comfort Height Toilet

• Elongated toilet bowl
• 1.28 gallons per flush
• Two-piece toilet
• Toilet dimensions: 27.25 x 17.62 x 30.5 inches

3. American Standard Cadet 3 Round Front Flowise Toilet

• Round toilet bowl
• 1.28 gallons per flush
• Two-piece toilet
• Toilet Dimensions: 26.2 x 17 x 29.1 inches

Best 12-inch Rough-In Toilets

If you are looking to replace an old toilet with a rough-in of 12 inches with a new one of the same rough-in, these are some of the best 12-inch rough-in toilets:

1. American Standard 2004314.020

• Round toilet bowl
• Rim height at 15.”
• 1.6 gallons per flush
• One-Piece
• Toilet dimensions: 17.75″D x 29.75″W x 28.5″H

2. HOROW HT1000 Dual Flush One Piece Toilet

• Compact Round Toilet
• Soft Closing Seat
• Fully Skirted
• 1.1 / 1.6 gallons per flush
• Toilet dimensions: 25 x 13.4 x 28.4 inches

3. American Standard 2462016.020 Cadet

• Round toilet bowl
• Standard 15″ Rim Height
• 1.6 gallons per flush
• Toilet dimensions: 30.25 x 20.5 x 29.25 inches

Best 14-inch Rough-In Toilets

If you are looking to replace an old toilet with a rough-in of 14 inches with a new one of the same rough-in, these are some of the best 14-inch rough-in toilets:

1. American Standard Cadet PRO Compact

• Round toilet bowl
• 6-1/2″ Rim Height
• 1.28 gallons per flush
• Two-piece toilet
• Toilet dimensions: 30.38 x 17.38 x 30.13 inches

2. Kohler K-3949-0 Highline Comfort Height Toilet

• Elongated toilet bowl
• 1.28 gallons per flush
• Toilet dimensions: 31-5/8 x 18-1/4 x 30-3/4 inches

3. Signature Hardware 447368 Bradenton

• Round toilet bowl
• 1.28 gallons per flush
• Toilet dimensions: 30.5″D x 17.25″W x 30.25″H

To check the prices and read a thorough review of these toilets, check out this post.

Conclusion

Measuring your toilet’s rough-in before buying a replacement is vital. You wouldn’t want to end up with a toilet you cannot install. Measuring a toilet rough-in is also so easy, and you surely don’t need to hire a plumber to do it for you.