A few years ago, I used that same calculator for my build:
Powered Driver Pulley Diameter: 1.05" small sheave
Driven Object Pulley Diameter: 9.55" large sheave
Belt Length: 44" L belt
Input (Driver) RPM: 1725 dryer motor
Resulting Output (Driven) RPM: 188.025
+1 On Copbrew133 & michaeltrego. CrankyBeaverBrewery if your new motors rpm is 1725 and you put the (for example) 1" pulley on the motor and the 10" pulley on the MM3 your new RPM would be around 172.
Your other option is to get a 10:1 90 degree gear box (ebay or surplus) and a love joy coupler from McMaster Carr and hook up your mill directly
Here is a link and this one too to a bunch of different ways people motorized their mills!