Bathroom Refit - do you cut bath to size

[DinosaurPuddles]

I'm hoping someone is either a bathroom fitter, knows a bathroom fitter or just generally an expert DIY-er.

I'm hoping to refit our bathroom once we're allowed. But I cannot figure out the bath size. The current bath is 1660 mm long and 700 mm wide at the narrowest part. Baths seem to come in 1600 x 700 or 1700 x 700. So where the hell has a 1660 x 700 bath come from? Or do you cut the bath down to size i.e. buy a 1700 and cut off 20 mm from each end? If anyone knows the answer please let me know. I don't really want a 1600 with a 40 mm insert but if that is the only way then I'll do it. I can't move the walls either and doubt I can cut into them that much.

Are you measuring the full length of your bath or just what's visible? Remember to allow for what's hidden under tiles.

I didn't think of that. I'm going from tile to tile. I still can't see how 40 mm would be hidden though but I know sizing can be deceptive.

Sometimes baths are set into a groove in the wall too.

Definitely don't cut it as you will lose the integrity of the bath.
If your bath is very old it could likely have been manufactured in imperial measurements.
Also where are you looking? Places like B&Q will have much less choice than a merchants will.

No, you don't cut the bath. In this instance the bath is inset into the wall. (This is how my old bath was installed when the house was built.) Apparently this actually helps, as it's easier to seal the gap and prevent water ingress.

It looks like you're intending to DIY? Maybe for that bit you can get professional help?

The other option is, as you say, to have a shorter bath with a shelf at the end to bridge the bath-to-wall gap. The advantage of that is you can have a removable bath panel and use the extra under-bath space as storage.

Presume this is wall to wall I think - 40 mm tiled area at the head end would be a useful shelf, I had about that much in an old en-suite in my parents house.