The SW toolbox has a ton of different sprockets, including chain sprockets, that you can configure about any way under the sun. No sketching needed!
Go to the toolbox, go to ANSI Inch, then Power Transmission, then Chain Sprockets, right click the chain sprocket type you want to create, and select create part.
It might take a bit of testing to figure out what the various parameters mean, but it's a much faster option than trying to draw gears or sprockets.
As for your original problem, you should know how many teeth the sprocket is to have. Divide 360 (degrees) by the number of teeth, and that will tell you the width of each tooth relative to the circumference of the entire circle.
Hope either of these suggestions help!