The broad ranges
A current BidetKing electronic-seat guide describes round bowls as commonly 16.5–17.5 inches and elongated bowls as greater than 18 inches from the bolt-hole centerline to the front edge. Its attachment guide uses a similar idea, with a slightly broader 16–17.5-inch round range.
A current TUSHY support page uses 18.5 inches as the dividing rule for its electric seats. That does not make one source wrong. It demonstrates that the product's actual dimensions and intended shape control.
| Your measurement | Broad interpretation | Next step |
|---|---|---|
| 16–17.5 in | Consistent with many round bowls | Compare with the exact round-seat drawing |
| 17.5–18.5 in | Borderline or compact elongated | Do not rely on category name; compare total seat and mounting dimensions |
| Over 18.5 in | Consistent with many elongated bowls | Still verify rear clearance and bolt spacing |
Overhang can be functional but awkward
A seat may mount and operate while extending beyond the front of a short bowl. That is not the same as a clean fit. Decide whether the seller considers overhang compatible, whether bumpers contact the porcelain correctly, and whether the return policy allows you to evaluate it without installation.
Shape is only one gate
Correct round or elongated sizing does not solve a French curve, inadequate rear clearance, unusual bolt spacing, inaccessible water connection, or missing outlet.