Door hinge bolt size?

This car keeps giving surprises: I put new lock cylinders in the doors (the doors were swapped before I bought it), and figured while I was there I'd try to adjust the doors because they sag. Well, hinges look to be in good shape, but each door seems to have only ONE bolt per hinge holding it on. So, what size bolts am I after? I'm hesitant to pull one of the existing ones to take to the shop because as I said, only one bolt per hinge.

Sheesh! Thanks again, folks!