Short answer
Choose a seat shape that matches the toilet bowl. An elongated bowl generally needs an elongated seat; a round bowl generally needs a round seat. BidetFit does not recommend mixing shapes as a workaround; an exact-model compatibility confirmation matters more than whether the bolts line up.
What manufacturers say
- Bio Bidet compatibility guide — says to match seat and bowl shape and explains why the bowl must support the seat.
- Bio Bidet “Will a bidet fit my toilet?” — describes measuring from the mounting-hole centerline to the front of the bowl, then checking bolt spacing and tank clearance.
Manufacturer sources checked September 13, 2026. These are general screens, not universal dimensions: use the exact toilet and seat drawings and ask the manufacturer about an unusual or uncertain match.
What to measure
- Bowl length: measure from the centerline of the seat mounting holes to the front of the bowl, then compare with the exact seat drawing.
- Bolt spacing and rear flat clearance for the seat housing.
- Whether the seat overhangs or leaves gaps after mounting.
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BidetFit is an independent information resource, not an installer or seller. No product was physically tested for this answer, and this guidance does not guarantee fit or installation. Send a question or correction.