Gearing

to find your wheel diamiter
700 cc rim = 622 mm

add tyre width x 2 (because tyre tend to be square

divide by 25.4 (mm in an inch)

e.g

for 23 mm tyre on a 700 cc wheel with a 48 x 16 your gear inches will be

(48 / 16) x ( (622 +(2 x 23) )/25.4 )

Try and use sproket with idealy a prime number of teeth or a sproket chain ring combo with as high as possible lowest demnomiator when the fraction is simplified to maximise skid patches. Clearly not a concern if you don't skid.

There is a mental person out side my window so I ust go now.