35 mm is the standard single tap hole, and almost every monobloc mixer is built for it. Some older ceramics are drilled at 32 mm, and a few kitchen sinks at 35 mm with a second 35 mm hole for a soap dispenser.
Measuring it
With the old tap removed, measure the diameter of the hole in the ceramic or the worktop. If the tap is still in place, the base of most mixers is wider than the hole, so the measurement has to wait.
The measurement people forget
Tail length. The threaded tails or flexible hoses that come down from the tap have to reach your isolating valves. A tap designed for a thin ceramic basin often has 30 cm tails; a thick stone worktop plus a deep vanity unit can put the valves 45 cm away. Extension hoses exist, and it is better to know before the tap is on the worktop.
And the one after that
Worktop thickness. The fixing stud has to pass through it and still take a nut. Makers state a maximum, and it is usually generous — but not always on a solid stone top.
Questions people actually ask
What if my hole is 32 mm and the tap is 35 mm?
The tap will not pass through. Ceramic can be enlarged with a diamond hole saw, which is a real risk of cracking the basin; a smaller-based tap is the safer answer.
What if the hole is larger than the tap base?
Cover plates and larger base washers exist for exactly this, and they are the normal solution when a three-hole basin is fitted with a single-lever mixer.
Last reviewed 5 September 2026