The basic equation is
where OBP is on-base percentage and SLG is slugging average. These averages are defined below as:
- the numerator "H + BB + HBP" effectively means "number of trips to first base at least"
- the denominator "AB + BB + SF + HBP" effectively means "total plate appearances", but does not include sacrifice bunts
This is because though a batter makes a trip to the plate he is not given an "AB" when he walks (BB or HBP) or when he hits the ball into play and is called out, but the action allows a run to score (SF). As a result, the 4 counts (AB + BB + SF +HBP) are needed to calculate a batter's total trips to the plate.
and
where:
In one equation, OPS can be represented as:
History[edit]
On-base plus slugging was first popularized in 1984 by John Thorn and Pete Palmer's book, The Hidden Game of Baseball.[2] The New York Times then began carrying the leaders in this statistic in its weekly "By the Numbers" box, a feature that continued for four years. Baseball journalist Peter Gammons used and evangelized the statistic, and other writers and broadcasters picked it up. The popularity of OPS gradually spread, and by 2004 it began appearing on Topps baseball cards.[3]
OPS was formerly sometimes known as production. For instance, production was included in early versions of Thorn's Total Baseball encyclopedia, and in the Strat-O-Matic Computer Baseball game. This term has fallen out of use.
OPS gained popularity because of the availability of its components, OBP and SLG, and that team OPS correlates well with team runs scored.
Criticism[edit]
Despite its simple calculation, OPS is a controversial measurement. OPS weighs on-base percentage and slugging percentage equally. However, on-base percentage correlates better with scoring runs.[9] Statistics such as wOBA build on this distinction using linear weights. Additionally, the components of OPS are not typically equal (league-average slugging percentages are usually 75–100 points higher than league-average on-base percentages). As a point of reference, the OPS for all of Major League Baseball in 2019 was .758.[10]