How to Properly Measure Your Space and Get the Right-Sized Toilet
Getting a new toilet? Great. Getting the wrong-sized toilet ? Not so great. Whether you’re replacing an old unit or upgrading to a smarter throne, here’s how to measure your bathroom space so you pick the right toilet the first time—no returns, no regrets.
1. Start with the Rough-In Measurement
The rough-in is the distance from the wall behind your toilet to the center of the floor drain (or the bolts that anchor the bowl).
Standard rough-in sizes:
- 12 inches – Most common
- 10 inches – Found in older homes or small spaces
- 14 inches – Less common, but available
How to measure it:
Measure from the finished wall (not baseboard) to the center of the bolts holding the toilet down.
If you're replacing a toilet, you’ll usually want to stick with the same rough-in size unless you're doing major plumbing work.
2. Know Your Bowl Shape: Round vs. Elongated
- Elongated bowls (about 18.5" long) offer more comfort
- Round bowls (about 16.5" long) save space in tight bathrooms
Measure from the mounting holes to the front edge of the bowl to confirm the size.
Pro tip: If your bathroom is compact, round bowls can help meet code and improve flow (the foot traffic kind).
3. Check for Side Clearance
Building codes typically require 15" from the toilet’s centerline to any wall or fixtureon either side.
Measure from the center of your floor bolts to the wall, vanity, or tub. You’ll need 30" total width minimum in most areas.
🔗International Residential Code toilet clearance guide
4. Consider Toilet Height
Standard height: 14"–15" Comfort/ADA height: 17"–19"
Comfort height is especially useful for taller users, older adults, or anyone with mobility issues.
Measure from the floor to the top of the seat (not the rim).
🔗American Standard guide: Choosing toilet height
5. Mind the Tank + Wall Clearance
If you’re tight on space, make sure your tank fits without bumping into anything behind it. Some modern toilets have slimmer tanks or even wall-mounted designs. Measure from the wall to the back of your existing tank, and compare it to the depth of your new toilet.