How to Measure a Toilet Seat for Replacement
Buying the wrong toilet seat is one of the most common (and most avoidable) bathroom shopping mistakes. Toilet seats aren't universal — get the shape, mounting spread, or seat post configuration wrong, and it simply won't fit. Here's exactly how to measure so you order the right seat the first time.
What you'll need
- A tape measure
- 5 minutes
- Your existing toilet seat removed (optional, but makes hinge-post measurement easier)
Step 1: Measure the bowl shape (round vs. elongated)
Measure from the center of the two hinge-post holes at the back of the bowl to the front edge of the bowl rim.
- Round bowls measure about 16.5 inches front to back.
- Elongated bowls measure about 18.5 inches front to back.
Not sure which you have? See our full Elongated vs. Round Toilet Seat guide for a side-by-side comparison and photos of each shape.
Step 2: Measure the hinge-post spread
Measure the distance between the centers of the two mounting holes on the bowl (where the seat bolts down). Most residential toilets in the U.S. use a standard spread of 5.5 inches, but it's worth double-checking — a mismatched spread is the #1 reason a "universal fit" seat doesn't actually fit.
Step 3: Check the seat post/mounting style
Most modern toilets use standard top-mount bolts (the seat bolts down from above, same as what you're replacing). Older or commercial toilets sometimes use a different post spacing or a side-mount hinge system — if your current seat looks unusual, bring a photo or the old seat itself when comparing options.
Step 4: Measure overall width (for wider or comfort-height bowls)
Standard bowls are about 14 inches wide at the widest point. If your toilet is a wider "comfort" or ADA-height model, confirm the width against the manufacturer spec sheet before ordering, since oversized bowls can sometimes need a specific wide-seat model.
Quick reference
| Measurement | Round | Elongated |
|---|---|---|
| Front-to-back length | ~16.5" | ~18.5" |
| Hinge-post spread | Standard: 5.5" (verify yours) | |
| Overall width | ~14" (standard bowls) | |
Shop by the numbers
Once you know your shape and spread, you can shop with confidence. We carry genuine Bemis toilet seats in both round and elongated fits, in plastic and enameled wood, with standard 5.5" hinge-post spacing on every model — including the Bemis Affinity Plastic Toilet Seat (elongated) and the Bemis Round Plastic Toilet Seat, both featuring Whisper-Close hinges so the seat never slams.
Still unsure after measuring? Send us your measurements and we'll help you find the exact match — no guessing, no returns.