Player Efficiency Rating (PER) is a per-minute rating of basketball performance originally developed by ESPN columnist John Hollinger. In Hollinger's words, PER "sums up all a player's positive accomplishments, subtracts the negative accomplishments, and returns a per-minute rating of a player's performance." The goal is to distill a player's total contribution on the court into a single number that can be used to compare players regardless of how many minutes they play.

PER accounts for both positive contributions (made shots, assists, rebounds, steals, blocks) and negative ones (missed shots, turnovers, fouls), weighting each based on its actual value in generating or preventing points. The calculation also adjusts for team pace, so players on fast-paced teams aren't unfairly boosted simply because their team takes more possessions. Finally, PER is standardized so that the league average is always 15.0, regardless of era. This makes it possible to meaningfully compare players across seasons. A PER of 20 represents the same level of above-average performance whether it was earned in 1985 or today.

Because some statistics weren't tracked in the NBA's earlier years (three-pointers began in 1979-80, turnovers in 1977-78, and offensive rebounds, steals, and blocks in 1973-74), calculating PER for older seasons requires reasonable estimates and substitutions for the missing data. This allows PER to be computed for every season dating back to 1951-52, when minutes played were first recorded.

For a full breakdown of the formula behind PER, see the following page: https://www.basketball-reference.com/about/per.html

On Basketball Reference player pages, PER is listed on the Advanced stats table.