A international convention declared that bike tires should have the actual size written as well as the vernacular. Thus you will see 622x35 at the very least. You will usually also see something like 700Cx35 or 700x35C, but this is not a measurement. The actual measurement is 622x35. Further complicating things is that 35 is not that the inflated width will be. For one thing, rim width affects inflated tire width. In theory, that spec is provided by the maker by measuring the bead-to-bead distance as the tire is flattened out and then dividing by 2.5.