The Ultimate Guide to Toilet Rough-in Dimensions

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Installing a new toilet feels like solving an equation with multiple variables. You need to learn unknown terms and processes, with toilet rough-in dimensions being one of the strangest.

But it’s not as hard as it seems because you can measure the rough-in very quickly. All you need is a measuring tape and some ground-level knowledge of your toilet’s position.

Let’s show you how!

What Is a Toilet Rough-In Size?

Toilet rough-in dimensions represent the distance between the center of the outlet drain and the wall behind your toilet. It’s important for two specific reasons:

  • The installation of a new toilet depends on the rough-in
  • If you can minimize the rough-in, you can free up space in your toilet room

But, why would you measure the toilet rough-in? 

Firstly, you probably do it because you want to replace the old toilet and install a new model. Secondly, you might start a bathroom remodeling project. The third option is that you want to make a second bathroom

In each case, knowing the exact distance between the back wall and the flange is vital for your plans. Now that you know it, let’s take a look at the three types of rough-ins.

Toilet Rough-in Common Dimensions

You can’t choose or set rough-in dimensions arbitrarily. Manufacturers follow industry standards, so you’ll always see one of these three rough-ins.

A 10-Inch Rough-in Toilet

A 10-inch rough-in is common in older houses and residential buildings. It simply means that the distance between the rare wall and the toilet’s outlet drain is 10 inches. It’s the smallest rough-in measurement you’ll find in a bathroom.

A 10-inch toilet rough-in is the best option if you want to save bathroom floor space. It’s not the most common type, but it’s worth a shot if you want to spare a couple of inches.

The best 10-inch rough-in toilets include models like Kohler Highline Comfort Height, TOTO Drake Tornado Flush, and American Standard Colony.

A 12-Inch Rough-in Toilet

Toilets with the 12-inch rough-in are by far the most popular. It is the standard toilet measurement, so you can expect these models to be cheaper than the other two types. 

Most brands focus on 12-inch rough-in toilets, giving you options with different features. For instance, the American Standard Normal Height toilet is one of the most affordable two-piece models. 

But you should check other toilets to see their design, water consumption, flush system, glazing, and other features. 

A 14-Inch Rough-in Toilet 

Toilets with a 14-inch rough-in are the rarest of all. You will probably find them in older households and residential buildings, but not in newer houses and flats. Apart from requiring more room, they aren’t different than the other two rough-in types.

Most manufacturers stopped making toilets with the 14-inch rough-in, but you can still find models like Kohler Highline Biscuit. It has an elongated toilet seat, providing more comfort for the elderly.

Kohler Highline Biscuit uses 1.28 gallons per flush, and it successfully handles even the hardest waste in the toilet bowl. It makes a good balance of water preservation and high efficiency.

Tools to Use When Measuring Rough-in Dimensions

It’s obvious that measuring the rough-in doesn’t require special tools, but you’ll need a few items to do it properly.

First of all, you must have a measuring tape. Any kind will do, but we recommend using a self-locking measuring tape because it helps you do everything alone.

Secondly, it’s good to have a pen and paper with you when measuring the toilet dimensions. That way, you can write down everything and scatch the bathroom outline if needed.

How to Measure Toilet Rough-in Dimensions?

Now you can start measuring the toilet rough-in. The way you do it depends on your toilet type, so we recognize three possibilities here.

Standard Toilets

Almost all modern toilets are standard models with a 12-inch rough-in. But you don’t want to take any chances – the toilet may surprise you with 10 or 14 inches between the back wall and the flange.

Read product specifications before buying a new toilet. Every manufacturer shares information about dimensions, including the toilet rough-in measurement. For instance, here’s how Kohler product specifications look like.

The most important detail is to measure the distance from the flange center to the finished wall. Don’t rely on baseboards and moldings – they are closer to the flange, so you can’t get the accurate measure.

The same goes for the stud wall. If it’s an inch thick, add it to the usual measure of 10, 12, or 14 inches. 

Corner Toilets

Corner toilets are specific because they don’t sit in the middle of the bathroom. On the contrary, they occupy the corner, and you need to measure the distance between both walls.

It doubles your work, but there’s nothing complicated about it – just measure the straight lines from the toilet flange to the walls. The two lines make a 90-degree angle and intersect.

The intersection point is in the flange center, and that’s where the rough-in ends. You will probably see that both lines make the same 12-inch distance (or 10/14 inches). That distance is the toilet rough-in.

Rear-Outlet Toilets

The Ultimate Guide to Toilet Rough-in Dimensions 1

Rear-outlet toilets are unusual because they don’t transfer waste through the vertical drain pipe. They rely on the horizontal wall drain, so you won’t measure the distance to the finished wall.

You’ll calculate the distance between the flange and the finished floor instead. The principle is the same, but the rough-in is usually shorter. That’s because wall-hanging toilets need a shorter outlet.

The bottom line is that your rare-outlet toilet will probably have the rough-in between five and nine inches.

3 More Things to Measure for Perfect Toilet Positioning

Another thing you need to remember is that measuring the rough-in is not the only task. If you want to install a new toilet, you have to measure additional details for perfect positioning. Let’s see how it works:

Left and Right Clearance

Do you feel comfortable in a bathroom so small that it gives you little to no space on the sides? We bet you don’t because every toilet needs a clearance on both sides of the toilet seat.

The same goes for both sides – there must be some room to the left and the right.  The general rule is to leave at least 15 inches from the toilet’s center on both sides. Larger bathrooms can provide more clearance space.

How do you measure a 15-inch clearance? The distance starts in the center of the toilet flange and ends a few inches outside the toilet. How much room is left on the side depends on the width of your toilet.

Floor Space in Front of the Toilet

You deserve the chance to stretch your legs while sitting on the bowl, so think about the space in front of the toilet. The distance to the finished floor varies according to the bathroom dimensions, but these are the basic rules:

  • 21 inches: The International Plumbing Code says 21 inches is the minimum for small toiler rooms and powder rooms
  • 24 inches: Traditional bathrooms must have at least 24 inches of free space in front of the toilet bowl

You should add at least a few more inches to the toilet room or your bathroom if possible. It won’t drastically change the outline of the room, but it will make your daily activities more comfortable and convenient.

Cold Water Supply Line Position

Your toilet needs a cold water supply line, so it’s necessary to think about its position as well. Most toilets require an L-shaped line that perfectly fits the standard rough-ins. It goes like this:

  • Identify the center of the toilet flange
  • Draw a six-inch line to the left side of the flange
  • Continue by drawing a line that goes up seven inches

The L-line with six- and seven-inch segments will suit most bathrooms – it goes well with the moldings, so you don’t need to make corrections in the waterline.  

Common Rough-in Measurement Mistakes

Measuring toilet rough-in dimensions is easy, but you can still make a few mistakes that interfere with installation plans. Three errors stand out:

Baseboard Rough-In Measurement

The most common mistake is measuring the distance from the toilet flange to the baseboard. This is not the right way to assess the rough-in because baseboards often lie a half-inch before the actual wall.

In other words, your calculation will be wrong, and you probably won’t buy the right equipment for your bathroom. Be careful and remember that the rough-in is the distance from the flange center to the wall behind the toilet. 

Toilet Bolt Calculation

Every toilet has a pair of toilet bolts connecting it to the bathroom floor. There’s one bolt on both sides of the bowl – they appear to point to the center of the flange. But that’s rarely the case as toilets have an unusual elliptic shape.

Instead of measuring the distance based on toilet bolts, do your best to identify the exact location of the toilet flange. When you do it like that, rest assured you won’t make a mistake while measuring the rough-in.

Bigger Toilet Models Equal More Space

You know that toilets come in different shapes, weights, and sizes. You can opt for an elongated or round toilet seat and bowl, but that doesn’t influence the rough-in position – most toilets have a standard waste outlet mechanism.

The same goes for toilets of different weights and sizes. Larger toilet bowls don’t necessarily mean you’ll need a longer rough-in. Remember that the final setup depends on the size of your bathroom and the position of the toilet flange.

The Bottom Line

A rough-in is not something you think about every day, but you have to analyze it before installing a new toilet. Modern toilets come with a standard 12-inch rough-in, but there are still some 10-inch and 14-inch models.

When you measure dimensions, don’t just focus on the rough-in. On the contrary, you should also check the side clearances, bowl front spacing, and the water supply line.

Perhaps it seems difficult, but it really isn’t – it will take a few minutes to measure everything on your own.


What is the code for toilet rough-in?

Toilet rough-ins can come in different dimensions, but the most popular is 12 inches. Besides that, you can sometimes find toilets with 10-inch and 14-inch rough-ins. The dimensions mainly depend on your drainage system and the bathroom size.  

How many inches should my toilet be from the wall?

Your toilet should probably be 12 inches from the wall because it’s the industry standard. However, you need to measure the distance between the back wall and the toilet flange. This is important because some toilets still have a 10 or 14-inch rough-in.

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