Toilet Dimensions for 8 Different Toilet Sizes (Diagrams)

Side profile of a toilet near a wooden screen in a modern bathroom.

The toilet may be a simple toilet appliance but it's one that many of us couldn't imagine living without. But even simple devises can have complicated features and finding the right toilet for your home can be a struggle. Kick your research off right by checking out this series of basic toilet dimensions, drawings, and definitions.

Oh, toilets, such incredibly imperative devices but devices that so few people ever talk about or discuss at length. You might even think that if you’ve seen one toilet, you’ve seen them all, or that the only thing worth deciding upon is whether you want fun and functional features like an integrated bidet or dual-flush capabilities. But pull in those reigns! There’s is so much more to consider when choosing what throne to add to your throne room.

Before you head to your local home improvement store or click over to an online retailer, it’s best to prepare yourself for a great array of choices. Toilets come in many different configurations, styles, and features, including features you may have never heard of.

For example, did you know that there are now fantastically effective self-cleaning toilets that have a section where you can add a heavy-duty cleaning solution? With these modern toilets, every time you flush, the throne enjoys a quick clean or you can press a setting for a deep clean cycle to get that porcelain truly sparkling.

However, while these extra features and components are incredibly important, the very first thing to look at is toilet dimensions. After all, you don’t want to get a toilet that’s so large guests hit their knees on the wall when they stand-up or you’re forced to give up your favorite side cabinetry for the excess space. You also don’t want to get a toilet that’s so small it makes the rest of your bathroom appliances and furnishings look comical. Then there’s also the height to consider. Too high and you’re tip-toeing even while sitting and too short and you might as well be squatting.

So how to find the just-right toilet dimensions? While every person and family is unique, we hope the following look at different toilet dimensions to help you get an idea of quality set-ups as well as how to set-up those toilets:

Related: Types of toilets

Back-to-Wall 1-PC

Back-to-Wall 1-PC diagram

If you’re looking for something simple and something practical, then you will really appreciate this single unit toilet. Created as one solitary piece, this Back-to-Wall 1-PC toilet is a great choice for the small guest bathroom or apartment bathroom, or for those trying to save space.

You can install the Back-to-Wall 1-PC toilet directly on a finished floor so long as you have the outgoing water pipe available to be installed at 12″ away from the finished wall. There is a 5.5″ gap between the finished wall and the bottom rearmost wall of the toilet. This allows for ample room to clean and reach as necessary the water valve for the incoming water to the top of the toilet supply tank. The pipe fitting for that water valve is likewise 5.5″ above the finished floor.

The Back-to-Wall 1-PC’s compact size offers several advantages including being easier to clean, being more durable due to their being less shifting components to brake, and having a sleeker, more modern design. This specific unit also comes with the dual-flush option. At the top of the tank, you’ll notice that there is a button for a “Half Flush” and a button for a “Full Flush”. Half flushes use significantly less water and ideal for removing liquid waste while full flushes are powerful enough for the removal of other waste.

Back-to-Wall Elongated 2-Piece Toilet

Back-to-Wall Elongated 2-Piece Toilet diagram

If you have a larger bathroom or taller family members who want something a bit more easy on the knees, then consider purchasing something with dimensions like this Back-to-Wall Elongated 2-Piece Toilet. And when it says elongated, it really does mean elongated. From the back of the wall to the forward-most tip of the toilet bowl, this toilet measures 30.5 inches — which is ideal for large bathrooms, but note that this toilet would feel cramped in many smaller half baths. The toilet seat itself spans 18.5 inches long and just under 14 inches at its widest.

In addition to being long, the Back-to-Wall Elongated 2-Piece Toilet also has some notable height advantages. The seat itself is 16.5 inches above the finished floor. This height allows most average to tall-sized adults to sit very comfortably atop the throne. Furthermore, unlike most compact toilets which have a lower tank behind the toilet bowl, this design allows for a fairly tall secondary unit behind its toilet bowl. Here, the top of the tank reaches an ample 30.75 inches above the finished floor.

Back-to-Wall Round Front 2-Piece Toilet

Back-to-Wall Round Front 2-Piece Toilet diagram

For those homeowners who want tall and wide but don’t like the extra-long look of the aforementioned elongated toilet, or who simply don’t have the space in their bathroom for such a model, consider the advantages of the more balanced Back-to-Wall Round Front 2-Piece Toilet.

This toilet is billed as two pieces but they connect snugly together to give the greater impression of one cohesive and nicely balanced unit. From the back of the wall to the forward-most tip of the toilet bowl, the Back-to-Wall Round Front 2-Piece Toilet measures 28.5 inches. This makes it a full two inches shorter than the aforementioned Back-to-Wall Elongated 2-Piece Toilet.

This toilet design features an incoming water supply valve that can be set in two positions. It also has the flush lever conveniently on the upper top left side just below where the 15.75-inch long toilet tank cover rests. This lever faces outward and thereby enables homeowners to put furnishing directly beside the toilet without having issues with people needing to reach to the side to push the flush lever. Note that unlike the first toilet design in our list that boasted the dual-flush mode for better water conservation, this design as it stands only allows for one-size-fits-all flushing capability.

Installation Basics

Installation Basics diagram

Picking your preferred toilet dimensions is only the very first step towards enjoying a new throne for your bathroom. The next step is understanding how to install it. We hope this basic installation design helps show how you need to place and secure your toilet in the set hole.

Unless you live in a repurposed commercial building, a homebuilt cabin that was designed before basic home zoning recommendations or you purposely decided to go against the grain when designing your own home, you should have an outgoing water pipe in your floor that will take all waste elimination away from your home and into either your septic system or onto your locality’s sewer treatment facility.

This outgoing hole is where you are going to be the central point of your toilet installation process as the holes absolutely must align and everything else can be more readily adjusted, such as adding extra length to your incoming water pipe.

Now that you know where to start, the next step is aligning the closet flange and the bottom of your toilet together so that the wax ring sits snugly within the inner diameter of the closet flange and the closet bolts come through. Note that you will need to apply the recommended manufacturer’s sealant around the entirety of the bottom of the toilet and especially around where the bowl will set on the closet flange. This will prevent any moisture from leaking out.

Once the closet bolts have gone through the necessary holes, place a tapered washer onto the bolt and secure down with an appropriately sized nut. Use a torque wrench to secure the nut and cover that nut with a bolt cap to prevent corrosion issues.

Next, it’s time to add the water tank portion of the toilet bowl. This will be done similarly to how you secured the toilet to the closet flange in that you’ll use the appropriately sized tank bolts, washers, and nuts to ensure that the pieces are fit and tightened securely down with a torque wrench. Pay special attention, however, to the rubber gasket in the included Installation diagram to prevent water leakage.

Wall Hung

Wall Hung diagram

For those who chose a more modern home design, are installing a toilet in a commercial business or a home repurposed from a commercial business, or who otherwise have a unique design, then you might not have a central sewer pipe out or you may be looking to move that.

In any case, the most popular alternative is to hang the toilet on the wall and have the outgoing sewer pipe placed alongside the incoming water pipe, which is to say have all the pipework in the wall and out of sight.

Wall Hung toilets are attractive as there’s no gunk or build-up that commonly happens at the base of the toilet because there is no base. Instead, the toilet is hung on the wall and the outgoing sewer pipe cuts through the wall and drains down and out. So where there should be a base, there is empty space, which has the other big benefit of making it much easier to clean floors.

Of course, while Wall Hung toilets make things a lot easier in the long-run, they can be frustrating to install. Because most of a person’s weight will rest on the Wall Hung toilet, it is incredibly important that you have it installed on strong through beams and if you aren’t especially handy, to have someone else do it for you. Installing a Wall-Hung toilet will also commonly require some demolition work as you’ll need full access to the backside of those beams to fully secure the fittings.

Wall Faced

Wall Faced

If you’re nervous about the strength of a Wall Hung toilet, then consider the balance this Wall Faced design offers. With this Wall Faced toilet you can enjoy that stable base that will offer ample weight support and you’ll enjoy the side benefit of having the actual water tank portion of the toilet hidden behind the wall.

Like with the Wall Hung toilet design, the Wall Faced toilet will also have the outlet waste pipeline going through the wall and exiting out. This can help prevent corrosion and leakage issues at the bottom base of the toilet. That said, you will still need to use some floor fixings to secure the toilet in place.

The design here has the toilet sitting about 550 centimeters out from the wall to the outermost tip of the toilet seat bowl. This makes the design a bit more compact compared to other options and a good choice if you’re concerned about space.

Water Closet / Toilet

Water Closet / Toilet diagram

This basic overall toilet dimension drawing helps showcase the key measurements that you will want to look at when researching and deciding upon which toilet you should buy. Note that these dimensions should primarily be used only when looking at traditional toilets that have a base that sits upon a finished floor and have an exit waste supply pipe going down from the floor.

For these dimensions, you are going to look foremost at measurement “A” and measurement “B”. “A” will be the length fro the finished floor to the very center of the water exit circumference. In other words, the center of where that closet flange will be placed and the bottom of the toilet secured. Measurement “B” will be the height of the toilet bowl.

This measurement is important as it will both determine how comfortable you, your family, and your guests will be when sitting atop the bowl and it will determine how your water supply piping will fit, for example, a higher toilet bowl seat will often mean longer water supply piping.

Water Tank

Water Tank diaggram

This dimension drawing showcases the various parts of your water tank. The most important part to seat correctly is that rubber gasket and ensuring that the tank to bowl gasket fits snug and there are no tears, cuts, or chips that might otherwise allow water leakage.

Once you have that gasket aligned, the next part is to secure the water supply line and screw down the bolts when installing. When installing the rest of the components of the toilet water tank, if they aren’t already installed, the best tip is to start at the bottom and go upward.

Your toilet’s handle fully controls when the water flushes out from the bottom bowl and new water from the tank gets replaced in. When you press down on the over, it lifts off the flush valve chain, and that lives the flapper allowing all of the water in the tank flood into the toilet bowl and thereby push out the excess waste. The rest of the components of the water tank are designed to ensure your tank fills up to the level necessary to complete that whole flushing process again.

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