A metric that estimates the percentage of offensive 2-point field goal attempts a defensive player blocks while he is on the court. Block Percentage can also be calculated for a team rather than an individual player.
In an effort to determine how much impact players have on their teams, sports statisticians have developed metrics such as Block Percentage. Blocked shots don't tell the entire story in terms of defensive effectiveness, but examining Block Percentage can give us clues as to how effective a player is on the defensive end, since about half of those shot attempts would have resulted in scores had the block not occurred.
Although the formula itself looks a bit more complicated, the basic idea is to look at all the 2-point field goal attempts a team had while a certain defensive player was in the game, and find the percentage of those possessions in which the defensive player blocked a shot. This value indicates, in part, how much defensive impact a player has on his opponents.