In baseball statistics, a player is credited with a plate appearance (denoted by PA) each time he completes a turn batting. Under Rule 5.04(c) of the Official Baseball Rules, a player completes a turn batting when he is put out or becomes a runner. This happens when he strikes out or is declared out before reaching first base; or when he reaches first base safely or is awarded first base (by a base on balls, hit by pitch, catcher's interference, or obstruction); or when he hits a fair ball which causes a preceding runner to be put out for the third out before he himself is put out or reaches first base safely (see also left on base, fielder's choice, force play). A very similar statistic, at bats, counts a subset of plate appearances that end under certain circumstances.
While at bats are used to calculate such important player hitting statistics as batting averages, slugging percentages and on-base percentages, plate appearances have no such statistical value. However, at season's end, a player must have accumulated 502 plate appearances during a season to be ranked in any of these categories. For example, suppose Player A, with 510 plate appearances and 400 at bats, gets 100 hits during the season and finishes with a .250 batting average. And suppose Player B, with 490 plate appearances and 400 at bats, gets 110 hits during the season and finishes the season with a .275 batting average. Player B, even though he had the same amount of at bats as Player A and even though his batting average is higher, will not be eligible for season-ending rankings because he did not accumulate the required 502 plate appearances, while Player A did and therefore will be eligible.
Rule 9.22(a) of the Official Baseball Rules make a single allowance to the minimum requirement of 502 plate appearances for the purposes of determining the batting, slugging or on-base percentage title. If a player:
he will win that title, but with his original statistic (before the extra at bats were added).
In the example above, Player B is 12 plate appearances short of the required 502, but were he be charged with 12 additional at bats, he would go 110-for-412 for a batting average of .267. If no one else has a batting average (similarly modified if appropriate) higher than .267, player B will be awarded the batting title (with his original batting average of .275) despite the lack of 502 plate appearances.
In a real-life example, in 2012, Melky Cabrera, then of the San Francisco Giants, finished the season with a league-high .346 batting average, but he had only 501 plate appearances, one short of the required 502. Per the rule, he would have won the batting title because after an extra at bat is added and his batting average recalculated, he still would have led the league in batting average. Cabrera's case, however, turned out differently. The reason Cabrera finished the season with only 501 at bats was because he was suspended in mid-August when he tested positive for illegal performance-enhancing drugs. Cabrera was still eligible for that extra plate appearance, but he requested that that extra plate appearance not be added to his total, and that he not be considered for the batting crown, because he admitted that his use of performance-enhancing drugs had given him an unfair advantage over other players. As a result, Cabrera's name is nowhere to be found on the list of 2012 National League batting leaders.
A batter is not credited with a plate appearance if, while batting, a preceding runner is put out on the basepaths for the third out in a way other than by the batter putting the ball into play (i.e., picked off, caught stealing). In this case, the same batter continues his turn batting in the next inning with no balls or strikes against him.
A batter may or may not be credited with a plate appearance (and possibly at bat) in the rare instance when he is replaced by a pinch hitter after having already started his turn at bat. Under Rule 9.15(b), the pinch hitter would receive the plate appearance (and potential of an at-bat) unless the original batter is replaced when having 2 strikes against him and the pinch hitter subsequently completes the strikeout, in which case the plate appearance and at-bat are charged to the first batter.
In common terminology, the term "at bat" is sometimes used to mean "plate appearance" (for example, "he fouled off the ball to keep the at bat alive"). The intent is usually clear from the context, although the term "official at bat" is sometimes used to explicitly refer to an at bat as distinguished from a plate appearance. However, terms such as turn at bat or time at bat are synonymous with plate appearance.
Official Baseball Rule 5.06(c) provides that "[a] batter has legally completed his time at bat when he is put out or becomes a runner" (emphasis added). The "time at bat" defined in this rule is more commonly referred to as a plate appearance, and the playing rules (Rules 1 through 8) uses the phrase "time at bat" in this sense (e.g. Rule 5.04(a)(3), which states that "[t]he first batter in each inning after the first inning shall be the player whose name follows that of the last player who legally completed his time at bat in the preceding inning" (emphasis added)). In contrast, the scoring rules uses the phrase "time at bat" to refer to the statistic at bat, defined in Rule 9.02(a)(1), but sometimes uses the phrase "official time at bat" or refers back to Rule 9.02(a)(1) when mentioning the statistic. The phrase "plate appearance" is used in Rules 9.22 and 9.23 dealing with batting titles and hitting streaks, but is not defined anywhere in the rulebook.
It is often erroneously cited that total plate appearances is the denominator used in calculating on-base percentage (OBP), an alternative measurement of a player's offensive performance; in reality, the OBP denominator does not include certain plate appearances, such as times reached via either catcher's interference or fielder's obstruction or sacrifice bunts (sacrifice flies are included).
Plate appearances are also used by scorers for "proving" a box score. Under Rule 9.03(c), the following two items should be equal for each team, because each is equal to the team's total number of plate appearances: