Streeter Lecka/Getty Images
Where B=Blocks, TMP=Team Minutes Played, MP=Minutes Played, OFGA=Opponent Field-Goal Attempts, O3PA=Opponent Three-Point Attempts
While having a player block a shot is useful, having a player block shots a higher percentage of the time is even more useful. Put quite simply, wouldn't you rather have a center rack up five blocks in 40 minutes played instead of taking 120 minutes of action to garner the same five blocks?
Block percentage takes this preference into account as it calculates the percentage of an opponent's two-point attempts that end up with the player in question blocking a shot.
This is one of the stats that we like to call "tempo-free," meaning that it's a stat adjusted for pace and volume.
A player going up against a fast-paced team like the Miami Heat or Washington Wizards is going to have more defensive opportunities to rack up counting stats, leading to elevated numbers of blocks per game and blocks per minute (which is also a better way of looking at blocks than just blocks by themselves).
Similarly, a player who plays 35 minutes per game is going to have more opportunities to put up impressive blocks numbers than a player on the court for 20 minutes per game. It may seem like common sense that averaging two blocks per game in 20 minutes of action per contest is more impressive than averaging two blocks per game in 35 minutes of action per contest, but that distinction is lost when only blocks per game is cited.
Because block percentage is free from the effects of pace and volume, it's a better indication of how effective a player is at racking up the rejections during each and every one of the team's possessions.
If that explanation sounded similar (or almost identical to the one provided for steal percentage), it's because it was. The two evaluations of performance do almost the same thing, just for different basic defensive stats.
Without looking at play-by-play data, the best this stat can do is provide an estimate of the aforementioned percentage it is meant to calculate.
The other problem is that it only takes two-point shots into account in the denominator while allowing for the possibility of blocked three-pointers in the numerator. The formula might have to assume otherwise because of the rarity of blocked three-pointers, but a successful block from outside the arc would add one to the blocked-shot total without a shot attempt being technically recorded in the formula.
This makes the stat slightly skewed in the positive direction.
"Bismack Biyombo has the best BLK% in the NBA right now with a mark of 9.2 percent, well ahead of JaVale McGee's second-place 7.9 percent."
How I interpret that sentence: One of the indications that Biyombo, a rookie for the Charlotte Bobcats, is going to become a productive player is that he's insanely efficient when it comes to blocking shots.