Πόντοι is just fine for speech in a non-professional environment. I think most people use it. In written form and for professionals like engineers, teachers, etc., εκατοστά is more common.
Δεκαπέντε πόντοι is not excepted as an optional translation. Is it too colloquial?
Well, without context πόντοι = points, so it's better to stick with εκατοστά. (And, for the record, the full word is εκατοστόμετρα! But it's a mouthful and not used at all really.)
Good to know, though! Thanks!
Just what I wanted to know about εκατοστόμετρο! thanks!
For the record, εκατοστόμετρα is marked wrong.