When selecting a toilet, whether for a bathroom renovation or replacing an old unit, getting the right size is crucial. Choosing the wrong size can lead to installation delays, additional costs, and even the hassle of returns. To avoid these issues, determining the correct toilet dimensions before purchasing is an essential step.
Ⅰ. Standard Toilet Dimensions
According to the International Plumbing Code (IPC), Uniform Plumbing Code (UPC), ANSI/NKBA Bathroom Planning Guidelines, ADA standards, and major toilet manufacturers such as Kohler, Toto, and American Standard, the key toilet dimensions are as follows:
1. Rough-in Size
- Standard size: 12 inches (common in modern homes)
- Special sizes: 10 inches or 14 inches (may be found in older homes)
2. Toilet Bowl Dimensions
- Bowl Width: 14 - 16.5 inches (typically refers to the widest part of the bowl, including the seat)
- Bowl Length:
Round Bowl: Approximately 16.5 inches
Elongated Bowl: Approximately 18.5 inches
- Seat Height:
Standard Height: 14 - 16 inches (seat height typically ranges from 15 - 16 inches)
Comfort/ADA Height: 17 - 19 inches (ideal for individuals with mobility challenges)
3. Toilet Tank Dimensions
- Tank Height: 27 - 31 inches
- Tank Width: 16 - 20 inches
- Tank Depth: 6 - 10 inches
4. Recommended Clearance Space
- Side clearance: The distance from the toilet centerline to the sidewall or other fixtures should be 15-18 inches, with ADA requiring a minimum of 15 inches.
-
Front clearance: At least 21 inches, though 24-30 inches is recommended for comfort. ADA requires a minimum of 48 inches.
- Water supply location: 8 1/4 inches above the floor and 6 inches from the toilet centerline.
- ADA-compliant design: An accessible bathroom should have at least a 60-inch turning space for wheelchair users.
* For standard residential use, these dimensions serve as a guideline for optimal comfort. However, if you are installing a toilet in a rental or resale property, ensure compliance with local building codes and city inspection requirements by consulting relevant regulations or a professional plumber.
Ⅱ. How to Measure Toilet Dimensions
1. Measuring the Rough-in Size
The rough-in size refers to the distance from the toilet’s waste outlet center to the wall behind it, which is a key factor in ensuring compatibility with your bathroom layout.
- How to measure:
Before removing the old toilet, measure the distance from the wall (excluding baseboards) to the center of the toilet’s mounting bolts.
* The IPC and UPC codes specify that toilet flange bolts must align properly with the toilet base to prevent leaks and ensure stability. Most manufacturers position the toilet flange bolts symmetrically with the waste pipe center for a secure and sealed installation.
2. Measuring the Bowl Length
The bowl length depends on its shape, with two common types: round and elongated.
- How to measure:
Start from the center of the seat mounting holes and measure to the front edge of the toilet bowl.
* Standard seat mounting hole spacing is 5 1/2 inches, with the midpoint at approximately 2 3/4 inches.
* Left - Simple Project ELEMAZ 21 inch Extra Tall Toilet | Elongated Bowl
* Right - Simple Project ELEMAZ 21 inch Extra Tall Toilet | Round Bowl
- Common bowl shapes and lengths:
Round bowl: 16.5 inches
Elongated bowl: 18.5 inches
The overall length from the back wall to the front of the toilet can be up to 31 inches for elongated models and 28 inches for round models.
TIP:
- Some manufacturers offer hybrid oval-shaped bowls(also known as oblong bowl) with in-between dimensions—refer to manufacturer specifications for exact sizing.
- Bowl length affects seat compatibility—round seats won’t fit elongated bowls and vice versa. Always check with the manufacturer before purchasing a replacement seat.
3. Measuring Seat Height
Seat height is the distance from the floor to the top edge of the toilet seat. Comfort is determined by how easily you can sit down and stand up.
- Standard seat height: 14 - 16 inches
- ADA-compliant height: 17 - 19 inches (also known as chair height, comfort height)
- Extra-tall toilets: 20 - 21 inches
* Different seat heights suit different users. Consider personal needs when choosing. If you're interested in learning more about toilet seat heights, check out our related articles.
· Chair Height Toilet vs. Extra Tall Toilet
· What is Extra Tall Toilet?
· Why Choose an Extra Tall Toilet for Elderly?
Note: Other measurements, such as bowl height (distance from the floor to the top of the ceramic bowl) and lid height (distance from the floor to the top of the closed lid), can sometimes be confused. Pay close attention to specifications when selecting a toilet.
4. Measuring the Tank Size
- Tank height: Measures from the base of the toilet to the top of the tank, usually between 27 - 31 inches.
* If you like to place plants, tissue boxes, or air fresheners on the tank, or if there are shelves, racks, or windows above it, ensure you have enough clearance.
- Tank width: Standard tanks (18-20 inches) offer stability and higher water capacity, while narrower tanks (16-18 inches) save space in smaller bathrooms.
- Tank depth: Standard tanks are 8-10 inches deep, ensuring sufficient water storage. Modern slim tanks (6-8 inches deep) provide a more compact aesthetic.
Ⅲ. Other Key Measurements
1. Flush System Components
- Trapway Size(ID):
4 inches: Improves flush performance and reduces clogging
3 inches: Standard for most households
- Flush valve flapper size:
2 inches: Common in traditional toilets
3 inches: More common in high-efficiency toilets
2. Inlet Pipe Size
This refers to the connection between the toilet's fill valve and the water supply line. The most common size in the U.S. is 7/8 inches. Simple Project Toilets come with a standard 7/8" adapter.
3. Plumbing Size
If installing a macerating toilet system with a macerator pump that connects to multiple bathroom fixtures such as a shower, sink, bathtub, or washing machine, ensure the inlet and outlet pipe sizes match the manufacturer’s specifications (e.g., SNFLEX Macerator Pumps).
* Compatible toilet systems: SNFLEX Two-Piece Macerating Toilet, SNFLEX 19" Extra Tall Macerating Toilet
* Compatible toilet systems: SNFLEX One-Piece Macerating Toilet
Conclusion
We hope this guide helps you select the right toilet for your bathroom! If you have any questions or need further advice on toilet sizing, feel free to contact us!