Originally Posted by dsbrantjr

Do a Google search on "bicycle gear calculator" Find one you like and play with it to get a feel for what effect various choices of sprockets and chainrings have. This one http://www.kstoerz.com/gearcalc/compare/ lets you compare two drivetrains so that you can, for example, compare your present setup with a proposed different one and see, graphically, the differences.