Informational Guide

How To Rough-In A Toilet (DIY Guide)

Toilet rough-in is an important measurement that you need to have a handle on before you try to DIY install a toilet.

by Ian Haynes

If you are going to do some work on your bathroom, then it is crucial that you have the right measurements.

Toilet rough-in is an important measurement that you need to have a handle on before you try to DIY install a toilet.

Here is a quick step-by-step guide on how to rough-in a toilet.

First, make sure that you measure the clearance behind the toilet. Get a tape measure, place the metal hook flush against the wall, and extend it to the middle of the flange mount. Ideally, you should be measuring something between 10” to 14”.

toilet rough-in

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Don’t worry if you are a little off. Toilets have a bit of flexibility with rough-in measurements, so don’t worry if it's not perfect. If you are measuring in an unfinished room, then make sure that you include the thickness of the drywall in your measurement. 

Next, you need to measure the clearance on the left and right of the flange. Starting from the wall on the left or right, place the hook of the measuring tape and pull it out, so it is perpendicular to the flange. As long as you have 15”, you are in a good spot. If there is less than 15”, then the best idea is to move the drainpipe or anything easy to move in the bathroom, like a vanity.

Third, it’s time to measure the space in front of your toilet. Place the measuring tape hook in the center of the flange and extend it out to the required distance. Usually, the required distance is around 21". Most toilet bases measure around between 12"-24", so make sure you add half of that measurement to the measurement of the space in front of the toilet.

Now it’s time to determine measurements for the water supply line. Starting from the center of the flange, measure about 6” to the left and go back all the way to the wall. Then, measure about 7 inches up from this spot and make a mark with a pencil or other utensil. This is where the water supply line will be installed.

Things to Know Before Getting Started

There are four major rough-in measurements that you need to know before you start trying to install a new toilet in your bathroom.

  1. 1
    The distance from the flange to the back wall
  2. 2
    The amount of clearance on the left of right
  3. 3
    How much space is in front of the bowl
  4. 4
    Where the cold water supply line goes

We will cover each of these in turn.

As far as the first measurement, the ideal distance is 12" though many toilets are made for 10" or 14" rough-in dimensions. Make sure that you measure from the wall itself, not from the siding that slightly juts out.

The minimum amount of clearance on the left or right of the toilet is 15”. There should be at least 15 inches between the toilet and any fixtures like the sink or tub on the left or right. Again, make sure you are measuring from the wall itself, not any baseboard that juts out of the wall.

The amount of space needed in front of the bowl depends on the plumbing code in your area. According to districts under the International Plumbing Code, then this distance is 21”. If you are under the Uniform Plumbing Code, then the measurement is 24”.

Lastly, the cold water line should be placed 6 inches to the left of the flange and about 7” up on the wall. As long as this point is above the baseboard of the floors, then you should be alright. If it is under 5”, then you might have to remove some of your baseboard moldings to install a cold water line. 

What Exactly is a “Toilet Rough-In”?

A toilet rough-in is a measurement that refers to the dimensions from the wall of the bathroom to the center of the holes that mount the flange on the floor.

The rough-in is an important measurement because the toilet you pick needs the right rough-in size, or else it will not sit in your bathroom property. 

Roughing in a toilet is important but pretty straightforward, so you can rough in a toilet by yourself, or you can hire a professional plumber.

Toilet Rough-In Standard Measurements

In general, the standard toilet rough-in dimension is 12”. Most toilets you can buy from the store are rated for a 12” toilet rough-in. Other common toilet rough-ins include 10” and 14”.

For the most part, any toilet can handle about 1 inch of variance in rough-in dimensions. If your rough-in is more than 14” or less than 10”, then you will probably have to buy a toilet specifically designed for a longer or shorter rough-in measurement.


What tools do I need to measure the toilet rough-in?

The only plumbing tools you will need to measure a rough-in is a tape measure and pencil for making markings.

How do I know if my toilet is 10, 12, or 14 inch rough-in?

Your toilet should say what its rough-in measurement is.

Can you replace a 14 inch with a 12 inch rough-in toilet?

Yes, usually you have a little bit of wiggle room in measurements. We would not recommend going more than 2 inches over or under, though.

How do you replace an old toilet’s measurements, 8 to 9 inches, with the standard toilet rough-in?

If you have an older toilet, then you just need to buy a toilet that has a slightly smaller rough-in, on the order of 10 inches.

How far should the toilet tank be from the wall?

There is no standard measurement, but most of the time, the toilet bowl will sit about a foot or 10" from the wall.

Can you move a toilet over a few inches?

Yes, if you have an offset flange, then you can move your toilet over a few inches. An offset flange will let you move the toilet without having to lay new pipes.

What is toilet offset measurement?

Offset measurement means how off-of-center the toilet is from the flange. Offset flanges are designed to let you move your toilet a few inches to the left or the right.


It’s essential to have the right measurements when attempting a toilet installation. Hopefully, our guide has assisted you in achieving the perfect home toilet installation.

Ian Haynes is an expert writer who has successfully deployed over 500 plumbing pages and other related content. He has an excellent understanding of home plumbing issues and translates his experiences via Plumbing Lab so readers can have a better understanding of common household problems. Outside of his work, Ian likes exploring Brooklyn with his Labrador.