From shape name to seat code
What do round and elongated mean for a seat?
Round and elongated are length classes. Kohler’s seat buying guide measures the seat from hinge to front; Bemis and TOTO measure the bowl from the mounting holes to the front and give the same figures.
Kohler says its elongated seats fit most elongated and compact elongated residential toilets. Bemis says in its FAQ that its seats are designed to fit most manufacturers’ round or elongated bowls, and adds that some specialty sizes exist.
Use the class to narrow the search, then ask for the seat named for the actual bowl.
| Maker and what is measured | Round | Elongated |
|---|---|---|
| Kohler: seat, hinge to front | 16¾ in or less | 18⅝ in or more |
| Bemis: bowl, mounting holes to front rim | About 16½ in | About 18½ in |
| TOTO fit chart: bowl, mounting holes to front | About 16-1/2 in (420 mm) | About 18-1/2 in (470 mm) |
How do you measure a bowl for a replacement seat?
Measure from the fixing holes. The first three steps follow Bemis’s measuring article; the last three add the measurements Duravit and American Standard name.
- Find the two mounting holes at the back of the bowl.
- Find the midpoint between the hole centres.
- Measure from that midpoint to the outside edge of the front rim.
- Measure the distance between the two hole centres.
- Measure the width of the bowl.
- For a bidet seat, measure from the tank to the seat holes.
American Standard asks for the tank-to-hole distance in its SpaLet measuring guide, with hole spacing and bowl length. Record the unit and both end points of every measurement.
How far apart are the seat fixing holes?
Bemis calls 5½ in standard and TOTO gives about 5-1/2 in (140 mm); Roca lists 200 mm for one Ona seat. Bemis says some seats will not match a toilet’s mounting-hole distance.
| Source | What it says |
|---|---|
| Bemis measuring article | Calls 5½ in the standard distance between mounting-hole centres. |
| TOTO WASHLET fit chart | About 5-1/2 in (140 mm) between hole centres, for most WASHLET models. |
| Roca, one Ona seat | For one discontinued Ona seat, lists 200 mm between bolt-hole centres, 430 mm from the holes to the bowl front and a 360 mm bowl width. |
| Duravit toilet-seat page | Names the distance between the mounting holes as one of three measurements. |
These figures are quoted from the makers named. This guide did not read a fixture standard for hole spacing, so measure the bowl.
Which seats are tied to a named bowl?
Some seats are sold against named toilets, not a size class. Duravit describes D-shaped, oval O-shaped and angular seats; it says the D shape is often used with wall-mounted toilets and calls the O shape probably the most common overall.
| Maker | How the seat is matched |
|---|---|
| Duravit | Its seat finder identifies the Duravit toilet and the seat compatible with it. |
| Roca | The page for one discontinued Ona seat lists three Ona toilets as compatible products. |
| Pressalit | Its FAQ says to search by manufacturer or by pan shape and dimensions. |
| Bemis | Seats designed to fit most makers’ round or elongated bowls; some specialty sizes exist. |
This guide found no source saying whether a D-shaped seat fits a bowl of another shape. Treat that as a question for the seat maker.
What else can stop a bidet seat fitting?
A bidet seat adds checks beyond length and hole spacing. The TOTO figures below are for its WASHLET seats, from its fit article and fit chart, not rules for other seats.
Tank clearance
On an elongated toilet, TOTO asks for at least 2 in from the tank front to the centre of the mounting holes.
Tank-to-bowl contours
TOTO’s fit chart notes that contours where the tank meets the bowl may stop a WASHLET fitting properly on some toilet styles.
Bowl width
TOTO asks for at least 8 in of open space from the toilet’s centre to the edge of the bowl’s flat surface.
Bowl size
American Standard says its SpaLet is designed to fit most elongated bowls but, depending on bowl size, it may not be possible to mount it.
Power
TOTO says a WASHLET needs a GFCI outlet within 3 feet of the toilet.
- Tank front to hole centres
- Tank-to-bowl junction shape
- Centre to flat-surface edge, and outlet position
What do a seat standard and the ADA cover?
One product standard and one accessibility rule name toilet seats directly. Neither replaces a fit check.
IAPMO/ANSI Z124.5
IAPMO’s list of current standards gives Z124.5-2013e1 (R2023) for plastic toilet seats, including seat covers. Its scope names materials, construction, performance testing and markings.
ADA 604.4, seat height
Section 604.4 of the ADA Standards, as published by the U.S. Access Board, sets the seat height of an accessible water closet at 17 in minimum and 19 in maximum above the finish floor, measured to the top of the seat. Seats must not be sprung to return to a lifted position.
ADA 604.4, exceptions
In residential dwelling units the permitted range is 15 in to 19 in. A single-occupant toilet room reached only through a private office, not for common or public use, is exempt.
The ADA height is measured to the top of the seat. Only the scope of Z124.5 was read for this guide; no dimension is attributed to it. Confirm which rules apply with the local authority.
What comes with a replacement seat?
The fixing parts and the seat functions depend on the named seat. Bemis says in its replacement article that each of its seats is packed with the appropriate hardware kit and instructions.
| Maker and product | What the maker says |
|---|---|
| TOTO SoftClose seat sheet | Two each of anchors, lock washers, round washers, screws and bracket covers; do not overtighten the screw. |
| Kohler seat ranges | Quiet-Close seats prevent slamming; Quick-Release seats come off without tools for cleaning. |
| Geberit toilet seats | A quick release for removing and reattaching the seat; a soft-closing seat. |
| Duravit toilet seats | Depending on the model, removable by hand without tools, for example with side push buttons; hinges in plastic or stainless steel. |
| Bemis, removing an old seat | Warns that tools can easily chip the porcelain of the bowl. |
How should a buyer order replacement seats?
These steps are procurement guidance, not a maker’s procedure.
- Identify the bowl. Record maker, series and model for every bowl variant on site.
- Measure from the holes. Hole spacing, length to the front rim and width, with units and a photo from above.
- Name the seat and kit. Ask for the seat code and the fixing kit together.
- Review bidet seats separately. Clearances, power and water need the seat maker’s requirements.
- Fit a sample. Name the bowl, the seat and the fixing used in the sample record.
- Keep the codes. File the approved seat and kit codes for later maintenance orders.
One result does not cover every bowl
A sample fit applies to the named bowl and seat. Do not extend it to other bowls because the shape name matches. Fixing route and access are covered in the related guide on top and bottom fixing.
What should you send and ask before a quotation?
A complete request names the bowl and the measurements, not only a shape.
| Question | Why it matters |
|---|---|
| Which bowl models is the seat stated to fit? | Some seats are sold against named toilets. |
| From which points is seat length given? | Kohler measures the seat; Bemis and TOTO the bowl. |
| What hole spacing does the seat accept? | Bemis says some seats will not match the bowl. |
| What is in the fixing kit? | Kit contents are stated per seat. |
| Which functions and standard are stated? | Ask for the document, not a label. |
Include with your request
- Toilet maker, series and model
- Hole spacing, length and width
- Photo of the bowl from above
- Tank or wall clearance behind the holes
- Quantity per bowl variant
WNS Global confirms any offered seat, fixing kit and commercial terms separately in writing. This guide does not state that WNS Global seats fit any named bowl, have any of the functions described or meet any standard or rule named above.
