Don’t Buy Another Toilet: Toilet Rough In Guide

Measure The Toilet Rough In Twice Before You Buy

Whether you’re remodeling your bathroom or wanting to update your toilet, it’s important to get the right measurements when roughing in your toilet waste and water. Fewer things are more frustrating than bringing home a new toilet, getting ready to install it, and realizing that the toilet dimensions are too big oflr too small and it won’t fit in the designated space.

Even if you think you can make the toilet fit, you’re likely to run into some major plumbing issues further down the road. It’s best to measure your toilet rough in right the first time. Below are some tips on how to perform a rough in plumbing for toilet.

Rough in Plumbing for Toilet Measurements and Standards: How to Measure Toilet Rough In and Toilet Dimensions (Inches)

When you are figuring out your toilet rough in dimensions, you will end up with one of three basic measurements. This is how to measure toilet rough in and toilet dimensions (inches).

10 Inch Rough In Toilet

If your bathroom is compact in size or you live in an older home, there’s a good chance that your toilet rough in size will be 10 inches. Due to the lack of space, you’re most likely to find that the toilet bowls are round front.

12 Inch Rough In Toilet

A 12 inch rough in is the most common measurement in bathrooms. This size allows for the most variety in the shape of the bowl and style of the toilet you purchase. Even though this is the most standard measurement, don’t forgo measuring (at least twice) before buying a new toilet.

12 rough in toilet

14 Inch Rough In Toilet

Much like a 10 inch rough in toilet, a 14 inch toilet is frequently found in small bathrooms of older homes. While your options will be limited, you still have some variety when looking at toilets.

What You Need To Know To Get Started

Getting started is easy as long as you take a little time to get organized before you take a quick measurement and race out to buy the first toilet you come across. Don’t forget to measure a few times to make sure your results are consistent.

Distance of Toilet Flange from Back Wall

When you install a toilet, you don’t want the back of it flush up against the wall. Correct measurements before installation will save you a lot of trouble. The toilet flange distance from wall (also known as a closet flange) is the pipe fitting which mounts a toilet to the floor, connecting the toilet drain to the drain pipe.

The distance of the toilet flange from the back wall depends on whether or not the construction is new or if a finished wall already exists. If a new wall has been framed in, but the drywall has not been hung, the distance from the toilet flange (center of the flange) to the wall framing should be at least 15 ½ inches. The standard distance from the back wall is 12 inches.

Necessary Clearance on Left and Right

Don’t forget to factor in the space needed for the left and right of the toilet. The minimum distance that you want on either side and measured from the centerline of the toilet is 15 inches. Whether there’s a wall on one side of the toilet or a fixture like a bathtub, 15 inches is the minimum.

Free Space Needed in Front of Bowl

If you’re working in a small bathroom you know that every inch counts for comfort and functionality; no one likes to sit down only to have their knees hitting the sink or wall in front of them. The minimum distance in front of the toilet, when facing a wall or fixture, is 21 inches. The more room, the better, but don’t make it any smaller than the minimum. Buying a toilet with a smaller, round bowl will fit into a compact space better than an elongated bowl.

Where To Place Cold Water Supply Line

An old water supply line to your toilet may start to corrode and leak, making a mess and wasting water. Whether you’re replacing the old line or installing a new one, placement is important. Water supply lines come in a variety of lengths, and you can use your old one as a template. It’s always better to buy too long than too short but avoid buying one that is so long that there’s extra hanging down from the tank; this could get tangled or damaged over time.

Water supply lines for toilets typically come out of the wall just under the toilet tank and on the side where the water inlet is located (usually the left side); cold water supply lines are often made out of copper and are about one-half-inch or three-quarter-inch thick. Sometimes you might see the water supply line coming out of the floor. Many people prefer the placement in the wall as it’s less noticeable. The water supply (either from the wall or floor) should be six inches high, and six inches offset to the left of the flange.

When you’re replacing the water supply line from the tank to the line in the wall, you will need to turn off the water and drain the tank. Be sure to shut off the valve and put a bucket underneath to catch any water that spills out one the tank is empty.

How To Measure Toilet Rough In and Toilet Flange Distance From Wall

Before you go ahead and start measuring it helps to know what roughing in is, right? In general, rough in can best be defined as the process of taking some measurements and laying out the groundwork before doing any of the actual work. Roughing in is used in all types of construction, electrical, and plumbing.

Getting the right measurements the first time will save you a lot of extra work and will make the whole process of installing a toilet that much easier. Follow these step-by-step instructions for measuring the toilet rough in: Remember, the center of the toilet flange to the wall should be 12 inches. Never measure from the molding (baseboard) to the flange, only against the wall. If you measure a few times and come up with 10 or 14 inches, you will need to replace with the proper size toilet.

If you want to measure before you remove the toilet and expose the flange, you will measure from the wall behind the toilet (not the baseboard) to the middle of the bolts on the toilet (closet bolts). Your measurements may not be 10, 12, or 14 on the dot but you can round up for the right dimension.

TPI Water Closet

Toilets with four bolts should be measured from the wall to the rear bolts. While this method is relatively accurate, your best measurement will come from measuring the distance between the center of the flange and the wall. When you’re determining the distance on each side of the toilet, your measurement should be at least 15 inches from the center of the flange (or the bowl) to the wall or fixture.

If you don’t have a finished wall, don’t forget to add a half-inch (or whatever the thickness of your drywall) to your measurement to account for the drywall. As you measure the distance from the front of your toilet to the fixture or wall in front of you, the distance will depend on your plumbing code. If your plumbing code is under the IPC (International Plumbing Code), your measurement should be a minimum of 21 inches.

If your code is under the UPC (Uniform Plumbing Code), your minimum measurement should be a minimum of 24 inches. Roughing in a water line should measure six inches to the left of the center of the flange and come up seven inches from the top of your finished floor. If the floor is unfinished, you will need to take the height of the flooring material into consideration.


  1. I have an old toilet with the flange being 10 inches. Which manufacturer sells units that would fit my space. I bought a standard toilet but the tank is too close to the wall. Consequently, I cannot line both screws to connect the tank to the bowl. Any suggestion would be most appreciated. By the way, this my first attempt at replacing a toilet. I’m not a very handy guy.

    1. Ask for a 10″ rough toilet that should do the trick. With regards to the closet flange, I would have to see the bolt pattern to give you an adequate assessment.

  2. help have a toilet that is far too small cistern does not reach wall , pan has four bolts 2 back 2 front i measured from the back wall to bolts at back it is roughly 42 cm what size of toilet would i go for converting it just over 16 inches

    1. You want to buy a 12″ rough toilet with a 4″x2″ offset closet collar. This will get you 2″ from the wall. Unless you can find a closet collar with a greater offset than 2″ I believe this is as close as you’ll get.

    1. Yes a 12″ rough toilet would be the one you would use. An offset closet collar would put you too close to the wall.

  3. I have an old Koehler 2 piece toilet. To check the rough in , since the toilet weighs 100 pounds, assembled, is it easy to detach the tank from the bowling then remove the bowl?

    1. That depends on what you consider easy. Because of the age of the toilet, there is probably some corrosion of the tank bolts. The tank may prove difficult to remove. Make sure you have the right replacement bolts ready when you reinstall the tank. As far as the bowl goes again if it’s been installed for 20 years the water closet bolts may be rusted. I would say remove with care.

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