I got curious, and since I still think in gear inches, I went back and ran the numbers on Sheldon's calculator. If you run 700 x 38 tires with 46x18 gearing, that would give you a 69.8-in gear, which is essentially a 70-in gear. Just for a historical perspective, that's close to what was the stock FIXED gear on pre-built British bikes sold out of catalogs, with typically a lower single-speed freewheel on the other side of the hub.
F.J. Camm in his 1936 book Every Cyclist's Handbook recommended around 65 gear-inches for men for a single-speed road bike, 60 gear inches for ladies. This was for general road work, including club runs and long rides.