Is it possible to change units on the app?

Yes, you can change the unit for each measurement that has been saved on the app.

Click on the measurement's "Kebab Menu"(①) and then "Change Units"(②) to select from mm, cm, inches(Decimal), and inches(Fraction)(③). 

Note: All measurements sent to the PIE app are originally saved in the unit that was used on the PIE device.