how to check gear ratio

[jbawgus]

i am trying to get all my peices together to do the swap. i just got the rear diff and i'm not 100% sure that it is 3.545, but it is out of a 02 wrx. i want to double check to make sure that the diff is 3.545 because the rear cover tag is missing, how do i do this.

[Splinter]

Turn the input shaft once and see how many times the axle stubs turn