checking to make sure my STEP_SCALE is correct

trying to remember from values i knew quite a while back...
my steppers are 1.8deg (200 per rev).
lead screw is direct drive, 5mm pitch, but my machine is in inches.
my stepper drivers are set, i think, to 1/8 microstepping (Leadshine DM542E, set to 1600 steps per rev).

my INI has STEP_SCALE values of 4063.9999 for all axis, but the machine is slow, so i want to verify. i have run the calculations so many times that i think i have forgotten how to calculate it...
so if i have this right: (8/1.*360*(5*2.54)= 20320 STEP_SCALE?

thanks in advance for this math help!
~Travis

200X8=1600
1600/5=320
That will be steps per mm, so multiply by 25.4
320X25.4=8128

wow, i was way off!!!

Many Thanks!!!

~Travis