Toilet Rough-In Sizes and Dimensions (Measure Like a Pro) 

Thanks in part to the Internet, inflation, and various other reasons, the DIY spirit is higher than ever in homeowners. As far as home projects go, one of the best places to save money is with your plumbing system. Certain plumbing fixtures, such as your toilet, are surprisingly easy to install or replace as long as you know how to rough them in and take the proper measurements. 

Taking the correct measurements and knowing what to look for is extremely important for roughing in a toilet. The most critical measurement you need to know is where the toilet flange is in relation to surrounding walls and obstacles. You can purchase the correct toilet for your bathroom with these measurements. 

While most standard toilets have the same rough-in measurements, there’s a chance that you don’t have a common toilet. A non-standard rough-in size is especially possible with older homes with outdated plumbing or wall-mounted toilets. If you’re interested in replacing your toilet all by your lonesome but aren’t sure where to start, you’ve come to the right place. 

What is a Toilet Rough-In? 

A toilet rough-in refers to the distance between the toilet drain pipe, the flange, and the back wall behind the toilet. This measurement is important during the rough-in process because there has to be enough room from the toilet to the finished wall behind it. Otherwise, the toilet won’t fit. 

Other measurements included during the rough-in stage include the distance from the flange to side walls and obstacles, but we’ll go into more detail on those later. 

Toilet Rough In Dimensions
Toilet Rough In Dimensions

Standard Toilet Dimensions 

Whether installing a new toilet from scratch or replacing an old one, you must know the typical measurements. A 12-inch rough is the most common rough-in measurement, but ten and 14-inch options are also available. 14-inch rough-ins are less common than their 12 and 10-inch counterparts. 10-inch rough-ins are especially popular for a small bathroom, a half-bath, or a powder room. 

Here are a few other standard toilet dimensions you should know about when purchasing a new toilet. 

Toilet Seat Height 

According to the international plumbing code, toilet seats must be between 17 and 19 inches high. If you plan to sell your home but get it inspected beforehand, you will fail your plumbing inspection if the toilet seat doesn’t fall within these dimensions. 

Toilet Tank Height

The toilet tank height refers to how high the top of the toilet tank is off the ground. The toilet tank height is much more open to interpretation and will depend on the type of toilet you have. Typically, the top of the tank can be anywhere between 21 and 31 inches tall, with one-piece toilets falling on the short side and tanked toilets being on the long side. 

Width of the Toilet 

The width of your toilet is essential if you fit it into a small space between walls or a wall and a vanity. There’s no uniform plumbing code saying how wide or narrow your toilet must be, but most toilets are around 20 inches wide. 

Toilet Depth

Toilet depth refers to how long your toilet is from the front to the back. The standard measurement for the depth of toilets is usually between 27 and 30 inches, depending on your toilet type and shape. Elongated bowl toilets are longer than standard ones but are the same width. 

What are the Standard Toilet Rough-In Measurements? 

Now that you know the standard toilet dimensions let’s look at the standard toilet rough-in measurements. 

Distance from the Toilet Flange to the Back Wall 

The distance from the center of the toilet flange to the stud wall behind it is the most crucial rough-in measurement and should be either 10, 12, or 14 inches, depending on the type of toilet you plan to install. Once the toilet gets set, there should be just enough room at the back of the toilet to remove the tank lid, and you shouldn’t press it up tight against the wall. 

Distance from the Toilet Flange to the Side Wall 

Once again, there’s no strict local plumbing code saying how much distance you should have from the side of the toilet to a wall or vanity. However, you should ensure a minimum clearance of 15 inches on all sides for your comfort. Fifteen inches of clearance is enough to clean around the side of the toilet and for a plumber to service your toilet when necessary. 

Distance from the Toilet Flange to Obstacles in the Front 

Typically, the distance from the front of your toilet to a wall won’t be an issue. However, if you don’t have much space to work with, you might run into trouble with having the toilet too close to the bathroom door. You should take this measurement into mind when installing or replacing your toilet so that you can easily access your bathroom. 

Location of the Water Line 

The location of the cold water supply line is one of the most important and overlooked aspects of roughing in a toilet. If you’re replacing an existing toilet, this measurement doesn’t matter. However, if you’re installing a toilet in a new bathroom from scratch, you should use a tape measure to place your water line 6″ to the left of the center of the flange and 7″ above the finished floor. 

How to Measure for a Toilet Rough-In Without a Toilet 

For our first scenario, let’s look at how to measure for a toilet rough-in if you don’t have an existing toilet to go off of. This situation applies to building a new house, building a new addition to your home, or adding a bathroom to your home. You can rough in your bathroom using these steps and measurements as a professional plumber would. 

  1. The first step of the rough-in process is to get yourself a good measuring tape. 
  1. Using the tape, measure 12″ from the wall behind where the toilet will be, outward. 
  1. Use a pencil or marker to mark this location, which will be the center of your toilet flange. 
  1. You can then either cut or drill a hole in the floor for the location of your toilet drain. 

Another option is to purchase and install the toilet yourself but leave the drain line installation to a professional plumber. If that’s the case, here’s what you need to do. 

  1. Use a tape measure to measure the distance from the wall behind the toilet to the center of the toilet flange. 
  1. If you have base molding, make sure that you mentally account for it or move your tape measurer above the molding when taking your measurement. 
  1. If a professional plumber installed your toilet originally, the measurement should be either 10, 12, or 14 inches. 
  1. If your measurement comes out as anything other than these three numbers, re-measure to make sure you measure correctly. 
  1. It’s not the end of the world if, for example, your measurement is 11″ instead of 10 or 12. The most straightforward way around this obstacle is to install a 10″ rough-in toilet, and you’ll have an extra inch of space behind the toilet. However, if this is too bothersome, you can search for a specialty toilet or extend your plumbing. 

This scenario also applies if you have an old toilet that needs to get replaced and you want to remove the toilet before taking rough-in measurements. 

How to Measure for a Toilet Rough-In With a Toilet

Measuring your toilet’s rough-in distance is slightly more difficult if you decide to measure before removing your toilet. It’s more challenging because you can’t see the toilet flange and won’t know exactly where the center is. However, if you find yourself in a situation where you need to purchase a new toilet before removing the old one, here’s what you need to know. 

Measure from finished wall to top of caps
  1. Locate the bolt caps on either side of the toilet. 
  1. Remove the bolt caps to see the bolts below holding your toilet in place. You should do this to ensure that what you’re seeing are the bolt caps. 
  1. Measure from the finished wall behind the toilet to the bolts or the center of the bolt caps. 
  1. The bolt caps are almost always directly in the centerline with the middle of the toilet flange and provide a reliable measurement for the rough-in. 

How to Measure a Corner Toilet Rough-In 

Corner toilets are a little bit trickier to measure for rough-in purposes. Corner toilets are standard toilets, but they’re tucked away in a corner, so you won’t be able to measure 12″ straight out from the back wall. However, if you have your heart set on putting your toilet in a corner, here’s what you do. 

Measure from back of finished wall to center of the drain pipe
  1. First, find the bolt caps on the existing toilet. 
  1. Next, look at your toilet from above and estimate the toilet flanges location based on the bolt caps on either side. Measuring in this way will take a little more guessing and estimation than other types of toilets, but you can still get close enough to make an accurate measurement. 
  1. Take a small piece of tape or something removable to put on top of your toilet seat to indicate the center of the flange. 
  1. Measure from the wall on either side of the toilet to get your rough-in measurement. 
  1. To ensure that you measure straight out from the wall, you can use a 2′ carpenters square. Press one side of the square flat against the wall so that the other endpoints straight at the center of the toilet. 
  1. Your measurement should be 10, 12, or 14 inches from either wall, but the two measurements should be identical. 

How to Choose the Right Toilet for Your Space 

Getting the rough-in measurement is the first and most crucial step to choosing a toilet that’s the right fit for your bathroom. However, as we discussed earlier, you also have to consider your toilet bowl’s depth, width, height, and shape. Getting a toilet that’s too long could prevent your bathroom door from opening and closing properly. 

You also don’t want a toilet bowl that’s too wide if your toilet gets wedged between walls or your shower and vanity. Remember, you should maintain a minimum of 15″ between the side of the toilet and obstacles to ensure you can service your toilet and access it easily. 

The toilet seat’s height and the bowl aren’t as big of a concern as long as you are between 17 and 19 inches to pass a plumbing inspection. However, the toilet tank is a more significant concern, especially if you have cabinets mounted behind the toilet. The tank should never be so tall that you can’t easily remove the lid and access the interior for servicing or repair purposes. 

Measuring for the Water Supply Line

Finally, you should never forget about the cold water supply line. This line is what will feed your toilet with a constant supply of water every time you flush it, and your toilet won’t operate without it. The location of the water line should be nondescript and blend into the background rather than standing out. 

  1. Measure 6 or 7 inches from the center of the flange to the toilet’s left side when facing the toilet. 
  1. From that spot, measure 6 or 7 inches up from the finished floor or where the finished floor will be. 
  1. Mark the spot on the wall with an X to indicate where your water line will stick out through the back wall. 

Related Questions 

Can I replace a 10-inch rough-in with a 12-inch one? 

In most cases, you won’t be able to replace a toilet set up for a 10-inch rough-in with a toilet set up for a 12-inch one. The 12-inch toilet will either be tight against the back wall, or the toilet flange won’t match the toilet drain. 

Can I replace a 12-inch rough-in with a 10-inch one? 

Although it isn’t ideal and might look too far away from the wall, you can technically replace a 12-inch rough-in with a toilet set up for a 10-inch one. Generally, you can always go smaller with a toilet but not always bigger. 

Do I measure the same way for a wall-mounted toilet? 

Wall-mounted toilets have rough-in measurements similar to standard toilets, but you’ll have to measure vertically from the floor up the wall rather than from the wall along the floor. 

Final Thoughts 

While measuring for a toilet rough-in is somewhat complicated and demanding, it’s well within the abilities of most people. The primary measurement to keep in mind is from the back wall to the center of the toilet flange. Once you have that measurement, the only things left to do are account for your water line and make sure the toilet you choose fits your bathroom space. The last thing you want is your toilet to appear bulky and out of place. 

Photo of author

Hubert Miles

I've been conducting home inspections for 17 years. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and FHA 203k Consultant. I started HomeInspectionInsider.com to help people better understand the home inspection process and answer questions about homeownership and home maintenance.
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