Stomach fullness is judged according to a discrete 7-step scale ranging from "nil" to "all". This scale translates into relative values between 0% and 100% represented by corresponding "points".

Stomach fullness of each individual i under investigation (i = 1, 2, 3.....n) is expressed by the stomach fullness index SFI_i on the points scale from 0-16 according to the ratio of volume of food in the stomach to stomach volume. The table below gives some orientation.