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Toilet Rough In: Make Your New Toilet Fit Perfectly!

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

So the opportunity to update and remodel your bathroom has come around and when the opportunity to rearrange or redecorate our bathrooms does happen, we jump at the chance.

But there’s more to remodeling a bathroom than just making it look good. You need to be precise in knowing what you need.

Plumbing (see also our article on indoor plumbing) issues usually always arise, and getting measurements wrong can cause even more problems, especially when it comes to the toilet. 

If you get the wrong measurements for your toilet, it can throw the entire design you envisioned off and that can really be a downer on the whole situation.

The same can be said for getting the wrong measurements of the toilet rough-ins… but what exactly is a toilet rough-in? 

In this article, we will be talking about something that is an imperative part of remodeling your bathroom successfully: “toilet rough ins”.

We will be going over what they are, and how you can make your toilet fit perfectly in your bathroom.

What Is A Toilet Rough In?

When it comes to fitting your toilet in your bathroom, you want to make sure that it’s comfortable, fits correctly, and isn’t at a slant or in the wrong place. The comfier the toilet, the better your bathroom experience will be. 

A Toilet Rough-In is the place of the water outlet, which is most commonly beneath the toilet. 

A lot of bathrooms have a rough-in already installed inside the wall, which can help you gauge what size toilet you need and where you need to place it. 

Taking The Placement Into Consideration

There are things you need to take into consideration when installing a new toilet and its placement. The main thing you want to make sure of is that it fits tightly against the wall with no gaps.

You have to take into consideration the size of your toilet as well. If you get the measurements wrong and you buy a smaller toilet, the toilet won’t fit as snuggly as a toilet of the correct size would.

If you have a larger toilet, it can cause problems too because there will be an odd-looking gap between the wall and the back of your toilet. 

If you have corner toilets (see also ‘7 Best Corner Toilets For Small Bathrooms‘), you need to make sure the measurements are precise too. 

There are no cutting corners with the measurements, you have to be accurate, otherwise, you run the risk of bigger problems down the road. But we will explain just how you do that in this article. 

Collecting The Right Tools

Before you even begin installing the toilet or the rough-in, you need to get your measurements done, you need to make sure you have the correct tools for the job.

You will need a pen and some paper to write the measurements down, but you can also keep a note of them on your phone if you’d rather do that. 

The main thing you will need is a measuring tool. The most common and easiest to obtain is of course a measuring tape, so make sure you have one of those on hand. 

Other than that, you don’t really need anything else for measuring, all you need to do now is actually measure the area you want for the placement of your toilet. 

Basic Measurements

Firstly, there are 3 standard sizes for toilets, each with a basic rough-in measurement. 

10-Inch Toilets

You will usually find 10-inch toilets in older homes, but they can be found in lots of other households as well. They are designed for compact size houses, usually smaller than other houses. The toilet bowls are usually found at the front. 

12-Inch Toilets

Of the three sizes, 12-inch toilets are the most common size found in houses. It comes in different shapes, sizes, and styles, fitting just perfectly into your bathroom. 

It is important to note, that just because this is the most common size, doesn’t mean you shouldn’t measure them. In fact, you should measure this size more than once just to be sure. 

Some sellers also don’t take 12-inch as a standard measurement, so you need to clarify this before buying a new toilet for your bathroom. 

14-Inch Toilets

14-Inch toilets are a lot like 10-Inch toilets, being found in older and smaller bathrooms. You can still find options in this size, but you are going to be more limited. 

Toilet Rough-In: Getting Started

You might think that measuring the toilet rough-in is going to be a really quick process, but this usually isn’t the case. Don’t rush, check all the measurements twice and keep yourself organized. 

There are three things you need to measure during this process: 

Toilet Flange Distance From The Wall

This step is important because if measured wrong, you risk damage to your walls. No one wants their toilet flush (see also ‘What Is Automatic Toilet Flusher And How Does It Work?’) to be right up against the wall. 

The closet flange fastens the toilet to the floor and connects it to the drain pipe

Toilet Rough In: Make Your New Toilet Fit Perfectly!

The correct measurement for this pipe fitting is 15 ½ inches. If you are just replacing the old toilet though, it should be 12 inches from the wall. 

Keep in mind that the measurements have a lot to do with if the construction is new or not, or if there is an already existing finished wall. The 15 ½ inch applies to the new framed wall and the 12 inch applies to the standard distance of an older wall. 

If the wall isn’t finished, add about half an inch to the distance you’ve already measured. 

Also, keep in mind the bolts on the toilet. Measure the distance between the back wall and the middle of the closest bolts to make sure the new toilet will fit in the place of the old one. 

Leave Space On The Left And Right

Next, you need to be mindful of the space on the left and right of the toilet. You need about 15 inches of space on both sides, measured from the centerline of the toilet. 

If there is a wall, a bathtub, or any other fixture around, the minimum space required is still 15 inches. 

Free Space In Front Of The Bowl

Every inch counts when installing anything in any room, but if you have smaller rooms, you may understand this a bit better. For comfort and functionality, you need space around your toilet. 

Imagine if you have already fitted your toilet into your bathroom and it looks like there’s enough space, but then when you sit on the toilet, you find that your legs are hitting a wall or a sink in front of you… this is not good for comfort and it’s not very functional at all. 

Even in smaller rooms, it is strongly advised to have as much space as you can between things. The minimum distance suggested for the free space in front of the toilet bowl is 21 inches.

It isn’t advised to go any smaller than 21 inches either. In this case, this is where buying a toilet that has a smaller, round bowl is better in a compact space and allows you the space you need with fewer complications. 

Cold Water Supply Line

Though it’s not absolutely necessary, you may want to check on your cold water supply line when you’re replacing your old toilet bowl

If the cold water supply line isn’t checked and maintained, it can corrode and leak, which can cause issues in the long run and also waste a lot of water. 

Cold water supply lines come in different lengths, so it is important to use your old one as a guide when checking and replacing it.

When you go to buy a new cold water supply line, don’t be surprised to see there are multiple lengths to choose from. 

The longer the supply line, the better in the long run, but make sure you don’t get one so long that it hangs down the tank. This is a risk because it can get damaged faster over time. 

If you’re struggling to work out where the cold water supply line is located, you can usually find it located under the toilet tank and where the water inlet is placed, which is just on the side.

Copper is usually used for these cold water supply lines and is usually between one and a half and three-quarter inch in thickness. 

Sometimes, the water supply line can be found in the floor, but most prefer it in the wall because it’s less noticeable.

Regardless of its wall or floor placement, cold water supply lines are preferred to be six inches high and 6 inches offset to the left of the flange. 

If you are replacing the water supply line, you must turn off the water and make sure it’s drained from the tank.

This is extremely important because if it’s the valve is not turned off, you risk it leaking on to the floor. Place a bucket underneath to collect any excess water that might spill out of the tank once it’s empty. 

Toilet Rough In (Standard)

Now you’re a bit more familiar with the measurements of a toilet, we can talk more about how to successfully measure the toilet rough-ins. 

We’ll start with the standard rough-ins. You have to be mindful not to misplace the measuring tape when working out this measurement.

You don’t want to measure the wall mold or the baseboard when it comes to finding out the measurements for the standard rough-in. 

You want to take the measuring tape and place it against the plaster or the wallpaper. Then, you want to pull the measuring tape to the other side of the toilet and keep it even.

Finally, measure all the way to the central bolt. You can find the central floor and waste outlet beneath the central bolt. 

Toilet Rough-In (Corner)

For corner rough-ins, you have to measure a bit differently from the standard rough-ins.

Corner rough-ins are a bit more complicated than the standard rough-ins, so you may want to measure it a second, or even a third time to make sure you have the correct measurements. 

The best and most right way to get the correct measurements is to measure from the central bolts to the wall.  Don’t measure the baseboard, but instead just measure from the wall. 

Once you’ve done this, repeat it again but on the other wall. 

You will have two measurements when this process is done and they will be exact. If you get different numbers for these measurements, it’s important to go back and measure again. 


Although this seems like a daunting task, measuring toilets and toilet rough-ins isn’t something you’ll be doing very often, and it’s better to just get it over and done with.

If you take your time and get it right the first time, you’ll save yourself a lot of stress and hassle than if you were to measure it wrong and buy the wrong toilet for the job. 

Having the wrong rough-in measurements can cause leaks when flushing the toilet, and that will just mean you’ll have to uninstall the whole toilet and you may have to spend even more money by getting a professional in to sort the problem out. 

Hopefully, this guide has helped you work out what you need for your toilet and its rough-in. If you follow the steps and keep the measurements precise, your new toilet will fit perfectly! 

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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