WPI:
WPI can be calculated from this equation of width.
No of needles=no of wales, and width is expressed in inch.
So, No of wales per inch=Total no of wales or no of needles/Width of the fabric in inches.
t is to be mentioned that actual WPI can be less than the WPI found from this equation if any needles are inactive.

Course Per Inch (CPI):

A knitted fabric is a combination of courses in horizontal direction with continuous yarn. A wale is formed having courses as shown in figure 5. A loop contains a tail yarn of previous loop and a head yarn of next loop [From figure 5], so effective height of every course is (d1-2dy) mm.

So, Course height is (d1 – 2dy) mm or { (d1 – 2dy)*39.36/1000 } inch
Let, n=no of courses required for 1 inch of fabric or CPI

This equation can be used to have idea of CPI or to determine required no of feeder/course.