String gauge question

[Peloquin]

This may be the silliest question so far but how do I tell what gauge strings I have on my bass? 

They are the strings it came with and I wasn't too get the same next time after struggling getting a lighter gauge on the last bass I had... loads of fret rattling so I had to get it set up. 

Is it simply a case of getting some verniers on the string?

Cheers folks. 

[warwickhunt]

If you have a lot of experience you can often have a very good guess what the gauge is if they are a regular set and not custom 'stepped' gauges but to know for sure you'd need a gauge.