Need some help with some math. Not your normal situation going on over here.
Ok, I got GT2 belt, 16 tooth pulley going to a 60 tooth pulley that is connected to a 16 pitch (24 tooth, 1.5 inch pitch diameter) spur gear on a rack and pinion setup. 1/16 stepping, 1.8 degree motor.
Bout to try and do the math…wish me luck
Ok, so…
1.5 x pi = 4.712 inches per revolution on the pinion
I have a 3.75 reduction with the 16 teeth to 60 teeth.
4.712/3.75 = 1.257 " per motor revolution
200/1.257 = 159.11 steps per inch
159.11 x 16 microstepping = 2545.76 steps per inch.
64,662.3 mm …oh dear what did I do wrong
You should just be able to do current steps/actual distance=x steps/desired distance.
Something like that, off the top of my head.
You are so very, very close. 
2540 steps per inch is 100 steps per mm.
Oh yeah what was I thinking.
Ok backup a bit
200/1.257 = 159.11 steps per inch
1 step divided by 159.11 inches = .00628 inches per step.
which is .1595 mm per step
Im looking for steps per mm so- 1/.1595 = 6.27 steps per mm
6.27 x 16x microstepping = 100.32 steps per mm
Yeah, current steps/actual distance=x steps/desired distance is what I will do once I bring my dial indicator home, just wanted to do the math and see how close it comes up. Ive laser cut my own rack and pinion setup and want to see how accurate it is coming out. Almost got a new machine up and running.