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Interactive Tool
Toilet Rough-In Size Calculator
Measure your bathroom to find the right rough-in size before you buy a new toilet.
How to Measure Your Rough-In
Find the wall behind your toilet
Look at the finished wall directly behind your toilet (not the baseboard). This is your reference point.
Locate the floor bolts
Find the two bolts (closet bolts) that secure your toilet to the floor. They are on either side of the toilet base, usually covered by small plastic caps.
Measure from the wall to the bolt center
Using a tape measure, measure from the finished wall (not the baseboard) to the center of the closet bolt. This distance is your rough-in.
Enter Your Measurement
What is a toilet rough-in?
The rough-in is the distance from the finished wall behind your toilet to the center of the drainpipe (measured at the closet bolts on the floor). It determines which toilets will physically fit in your bathroom.
Standard rough-in sizes
| Size | Prevalence | Notes |
|---|---|---|
| 12-inch | ~85% of homes | Standard in homes built after 1950s. Widest toilet selection. |
| 10-inch | ~10% of homes | Common in older homes and small bathrooms. Fewer options. |
| 14-inch | ~5% of homes | Found in some older homes. Most limited selection. |
Common measurement mistakes
- Measuring from the baseboard instead of the finished wall — this will give you a shorter reading. Remove the baseboard measurement from your total if needed.
- Measuring to the wrong bolt — measure to the bolt closest to the wall, not the front mounting bolt.
- Measuring with the toilet removed — if the toilet is removed, measure from the wall to the center of the drainpipe in the floor.
How we rank & our data sources
We do not run physical lab tests. Rankings are built from published, verifiable data and real owner feedback, never paid placement.
- MaP (Maximum Performance) flush scores
- EPA WaterSense certification & GPF ratings
- Manufacturer specifications (trapway size, flush-valve, rough-in)
- Verified owner reviews from Amazon, Home Depot & Lowe’s
Researched by admin · Last updated August 8, 2026 · Our review method
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