The PEI index is designed to provide an overall summary evaluation of expert perceptions that an election meets international standards and global norms. It is generated at the individual level using experts' answers to the 47 substantive variables. Mean substitution is used at the expert level to fill missing data. The 47 scores are summed and then standardized on a 100-point scale.

Starting from PEI 10.0, they reduced the number of questions included in this calculation from 49 to 47. The two deleted variables are postal voting and internet voting availability. These were removed since authors do not believe them to be essential to electoral integrity, since a variety of convenience voting methods are available in countries.