NEMA has standard frame sizes and dimensions designating the height of the shaft, the distance between mounting bolt holes and various other measurements. The integral AC motor NEMA sizes run from 143T- 445T, and the centre of the shaft height in inches can be figured by taking the first two digits of the frame number and dividing it by 4.

The fractional horsepower motors, for which NEMA spells out dimensions, utilise 42, 48 and 56 frames whose shaft height in inches is figured by dividing the frame number by 16.