How to Measure a Toilet for Replacement? – 4 Steps

Written by

Paulk Webb


Freddie J. Hagopian

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how to measure a toilet for replacement

A variety of reasons cause the need for a new toilet. Did the old one break? or do you simply want an upgrade for more efficiency? You can also renovate your bathroom.

Whichever it is, you must take care of the measurements for a smooth installation process.

This article will guide you on how to measure a toilet for replacement; determining the rough-ins, the size and height of the toilet, and other things you need to know to pick and put in the new commode successfully.

Step-By-Step Guide to Measure for a Toilet Replacement

What you will need:

  • tape measure

Before we begin, the measuring happens without removing the toilet. This is easier, especially if the new toilet has to match the old one’s dimensions. If you’re going for an entirely new upgrade, you can use the old commode as your basis too.

Step 1: Measure the Toilet Rough-in

The required distance and space allowance is essential to measure to replace a toilet. You have to ensure that there’s enough room for installation and movement when in use.


1. The rough-in is supposedly the distance between the wall behind the toilet to the center of the flange.

To determine the toilet rough-in size, measure from the wall to the bolts that secure the commode to the ground.

2. There are three available rough-in measurements in inches: 10”, 12”, and 14”. If the result on the first step is not exact, then stick to the closest number to the sizes above.

For example, if your measurement is:

  • 5” (between 10” and 11”) – pick 10”
  • 5” or 12.5” (between 11” and 13”) – pick 12”
  • 13” or 13.5” – pick 14”

Step 2: Calculate the Bowl’s Height


You may purchase a standard-height toilet or upgrade to a taller commode. Either way, measuring toilet dimensions is essential; it may be too high that your head will bump into the shelf above the wall!

1. With the tape measure, place the end on the floor and up to the old toilet’s seat.

Standard commodes are below 17 inches; those beyond that are considered comfort height toilets.

2. We also recommend measuring from the floor to the bowl only, since some toilet brands exclude the toilet seats from the total height.

Step 3: Take the Tank’s Height

Contributing to the toilet’s entire height, we have to make sure that the tank doesn’t hit the shelves or racks on the wall behind.

  • Take your tape measure and start running it from the ground up to the top of the old toilet tank’s lid.

Step 4: Determine the Toilet Bowl Size

Finally, the depth is the last of what makes up the full commode size. We have to make sure that it doesn’t hit objects at the front and sides, and that there is space for the user to get through.

1. Open your old toilet bowl’s seat cover before measuring the depth and width of the commode.

2. Starting with the depth, run the tape measure from the seat bolt holes—or the holes where the toilet seat’s screws rest—to the front edge of the toilet seat.

The result can be either of the two:

  • Round Seat (Standard Size) – around 16 ½ inches
  • Elongated Seat – around 18 ½ inches

3. The last step to measure a toilet seat is to get the width. To do this, measure from each edge of the pan or the right and left sides of the seat.

Assess Other Considerations

After performing measurements of the old toilet as the basis when buying a new one, there are a few more things that you should take into account to achieve the best bathroom (that follows laws!).

1. Toilet Clearance


Defined as the space around the commode, the toilet clearance varies depending on local building codes. Aside from following the rough-in measurements tacked in the first step, here are the other minimum measurements you must consider:

  • From the toilet’s centerline to the walls or obstacles on both sides – 15 inches distance. We recommend leaving 18 inches of distance between the toilet and another bathroom fixture.
  • Between the toilet’s centerline and another bathroom fixture (e.g. bathtub) – 18 inches distance
  • From the toilet’s centerline to the wall or obstacle in front of the toilet – 21 inches distance

2. Grab Bars (Optional)


Suppose you’re someone with mobility issues caused by age or an injury. In that case, you might be planning to place grab bars around the toilet for accessibility and safety.

The installation of grab bars should abide by the requirements of the Americans with Disabilities Act of 1990 or “ADA.” Some of which you must consider are the following:

  • spacing (between the grab bar and the wall; between the grab bar and protruding objects above, below, and in front)
  • diameter, dimension, and perimeter
  • place of installation
  • position of installation (side and rear wall)

If you wish to learn more about the detailed requirements of the ADA regarding the setting up of grab bars, we provide complete information on where they should be placed.


It’s easy to find your way around how to measure a toilet for replacement as you only have to focus on four things: rough-in, bowl’s height, tank’s height, plus the seat’s depth and width.

Measuring the rough-in goes from the wall behind the commode and the latter’s bolts on the base. The bowl’s height starts from the floor to the seat. On the other hand, the tank’s height starts from the floor up to the tank’s lid. Lastly, measure the seat’s depth and width.

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