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