How are coaxial cable connectors sized?
There are no 'standard' crimp connectors. Crimp connectors are designed for a specific type of cable, eg RG178. This is why distributors allow you to search by cable type.

Soldered connectors are more forgiving, you can take up more tolerances.

Once you've done your homework, and tabulated the dimensions of all popular cable types (wikipedia 'coaxial cable' is a good place to start, along with cable manufacturer sites), then you can see if the particular cable you have has an equivalent.

It may be better (frequency range permitting) to buy a connector/cable combination you can get, and then splice the cable you have. As a tip, what I often do is to buy a cheap BNC coaxial cable assembly, cut it in half, and then have two 'pre-wired' connectors with coaxial tails. Obviously a coax splice is only going to work well up to some frequency short of the capability of the connectors, but with care it can work surprisingly well.