Toilet Sizes: Elongated vs Round, Height and Rough-In
Elongated bowls are about two inches longer than round ones, chair height means a 17 to 19 inch seat, and the rough-in must match your floor drain.
By Karson AbernathyContributing writer.
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The short answer
Three measurements decide whether a toilet fits your bathroom and your body: the bowl shape, the seat height and the rough-in. A fourth number, gallons per flush, decides how much water it uses.
Elongated vs round toilet
The difference is the bowl length, measured from the center of the seat bolt holes to the front of the bowl. A fit guide from bidet seat maker Brondell gives 18 to 19.5 inches for an elongated bowl and 16 to 17.75 inches for a round one, so an elongated bowl reaches about two inches further into the room.
Elongated bowls give more room to sit. Round bowls take less floor space, which helps in a small bathroom or where the door swings close to the toilet. Seats and bidet seats are sold by bowl shape, so measure before you buy one.
On Wiki Shopping, 316 of the 451 toilets listed on October 26, 2026 state a bowl shape: 257 are elongated and 59 are round.
What is a comfort height toilet?
Comfort height, chair height and similar names describe a taller bowl. The useful number is the seat height, measured from the floor to the top of the seat. The 2010 ADA Standards for Accessible Design set 17 to 19 inches for accessible toilets, and allow 15 to 19 inches inside homes. A taller seat means less distance to lower yourself and to stand back up; a lower one can suit children and shorter adults.
| Seat height on Wiki Shopping | Toilets |
|---|---|
| Chair height | 164 |
| Extra tall | 25 |
| Standard height | 5 |
How to measure toilet rough-in
The rough-in is the distance from the wall behind the toilet to the center of the drain, which sits under the toilet. With the old toilet still in place, measure from the finished wall (not the baseboard) to the center of one of the bolts that hold the toilet to the floor. A new toilet must match that distance.
Among the toilets on Wiki Shopping that state a rough-in, 78 are made for 12 inches and 18 for 10 inches.
Flush ratings
The flush rating is the water used per flush, in gallons per flush (gpf). The EPA says the federal standard allows 1.6 gpf, and toilets with its WaterSense label use 1.28 gpf or less, 20 percent below the standard. Older toilets can use as much as 6 gallons. Dual-flush toilets have a full flush and a smaller one for liquid waste.
| Flush volume on Wiki Shopping | Toilets |
|---|---|
| Under 1.2 gpf | 24 |
| 1.2 to 1.4 gpf | 161 |
| 1.5 to 1.6 gpf | 67 |
We also list 152 dual-flush toilets and 166 toilets with a bidet built in or included.
How we count
Each toilet on Wiki Shopping has its bowl shape, seat height, rough-in and flush volume read from the store listing. Toilets whose listing does not state a value are left out of that count. Counts change as listings change.
Shop by spec
Toilets
Elongated, 1.2 to 1.4 GPF, Chair height
- ✅ 30-1/8"L x 21-1/4"W x 31-1/4"H
- ✅ Pressure Assist flushing system
- ✅ Two-piece
- ✅ Elongated bowl
- ✅ 12" rough in
Chair height
- ✅ Kohler Part
- ✅ Kohler K-3578-RA-7 Barrington Pressure Lite, Comfort Height Toilet with Right-Hand Trip Lever, Black Black
Two-piece, Elongated, 1.5 to 1.6 GPF, Chair height
- Two-piece configuration eases installation and maintenance
- Elongated bowls provide an extra 1-1/2-in compared to the traditional round bowl
- Covered under Kohler's 1-year limited warranty
- Floor mounted for easy installation
- Comfort height providing a higher seat, sometimes referred to as a handicapped toilet, it is designed for ease of use
Two-piece, Round, 1.2 to 1.4 GPF, Chair height
- Two-piece toilet
- Round-front bowl offers an ideal solution for smaller baths and powder rooms
- Comfort height feature offers chair-height seating that makes sitting down and standing up easier for most adults