Take three measurements with the old seat removed: hinge hole spacing, length, and width. Nearly every complaint about a toilet seat is one of these taken wrong or not taken at all.
1. Hinge hole spacing
The distance between the centres of the two holes in the ceramic. On European pans this is close to universal at around 155 mm, but it is the first thing to confirm rather than assume.
2. Length
From the centre line of the hinge holes to the outside front edge of the pan. This is the measurement that makes a seat look right or wrong, and it varies from roughly 40 to 48 cm across ordinary pans.
3. Width
At the widest point of the pan, across the bowl. It settles the shape — oval, D-shape or square — which is otherwise guessed from a photograph.
Why the seat has to come off
The old seat overhangs the ceramic, so every measurement taken with it in place is a measurement of the seat you already have rather than of the pan.
Questions people actually ask
Are toilet seats a standard size?
The hinge spacing very nearly is; the length and width are not. That is why two seats that both fit the holes can look completely different on the same pan.
What is quick-release and is it worth it?
It is a hinge that lets the seat lift off without tools, for cleaning underneath. It costs a little more and it is the feature people miss most once they have had it.
Last reviewed 5 September 2026