Onbase plus slugging
Onbase plus slugging (OPS) is a sabermetric baseball statistic calculated as the sum of a player's onbase percentage and slugging average.^{[1]} The ability of a player both to get on base and to hit for power, two important offensive skills, are represented. An OPS of .900 or higher in Major League Baseball puts the player in the upper echelon of hitters. Typically, the league leader in OPS will score near, and sometimes above, the 1.000 mark.
Contents
Equation
The basic equation is
OPS = OBP + SLG \,
where OBP is onbase percentage and SLG is slugging average. These averages are defined
SLG = \frac{TB} {AB}
and
OBP = \frac{H+BB+HBP} {AB+BB+SF+HBP}
where:
 H = Hits
 BB = Base on balls
 HBP = Times hit by pitch
 AB = At bats
 SF = Sacrifice flies
 TB = Total bases
In one equation, OPS can be represented as:
OPS = \frac{AB*(H+BB+HBP)+TB*(AB+BB+SF+HBP)}{AB*(AB+BB+SF+HBP)}
Interpretation of OPS
OPS does not present a complete picture of a player's offensive contributions. Factors such as baserunning, basestealing, and the leverage/timeliness of performance are not considered.
More expansive sabermetric measurements do attempt to incorporate some or all of the abovementioned factors. Nonetheless, even though it does not include them, OPS correlates quite well with team run scoring.
Other sabermetric stats, such as runs created and Wins Above Replacement, attempt to express a player's contribution directly in terms of runs and/or wins. However, a player's OPS does not have a simple intrinsic meaning.
OPS is a convenient calculation, but presents several issues. OPS weighs onbase percentage and slugging average equally. However, onbase percentage correlates better with scoring runs.^{[2]} Statistics such as wOBA build on this distinction using linear weights. Additionally, the components of OPS are not typically equal (leagueaverage slugging percentages are usually 75100 points higher than leagueaverage onbase percentages). As a point of reference, the OPS for all of Major League Baseball in 2008 was .749.^{[3]} Furthermore, despite being based on two already wellestablished stats and thus easy to calculate, the calculation does not follow mathematical rules of addition with fractions; i.e., the denominator for onbase percentage is plate appearances while the denominator for slugging percentage is at bats.
An OPS scale
Bill James, in his essay titled "The 96 Families of Hitters"^{[4]} uses seven different categories for classification by OPS:
Category  Classification  OPS Range 

A  Great  .9000 and Higher 
B  Very Good  .8333 to .8999 
C  Above Average  .7667 to .8333 
D  Average  .7000 to .7666 
E  Below Average  .6334 to .6999 
F  Poor  .5667 to .6333 
G  Atrocious  .5666 and Lower 
This effectively transforms OPS into a 7point ordinal scale. Substituting quality labels such as Excellent (A), Very Good (B), Good (C), Average (D), Fair (E), Poor (F) and Very Poor (G) for the AG categories creates a subjective reference for OPS values.
History
Onbase plus slugging was first popularized in 1984 by John Thorn and Pete Palmer's book, The Hidden Game of Baseball.^{[5]} 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.^{[6]}
OPS was formerly sometimes known as "Production", for instance in early versions of Thorn's Total Baseball encyclopedia, and in the StratOMatic computer baseball game. This term has fallen out of use.
Leaders
The Top 10 Major League Baseball players in lifetime OPS, with at least 3,000 plate appearances through the end of the 2014 season are (active players in bold):
 Babe Ruth, 1.1636
 Ted Williams, 1.1155
 Lou Gehrig, 1.0798
 Barry Bonds, 1.0512
 Jimmie Foxx, 1.0376
 Hank Greenberg, 1.0169
 Rogers Hornsby, 1.0103
 Manny Ramírez, 0.9960
 Albert Pujols, 0.9914
 Mark McGwire, 0.9823
The top four were all lefthanded batters. Jimmie Foxx has the highest career OPS for a righthanded batter.
Source: BaseballReference.com  Career Leaders & Records for OPS
The Top 10 singleseason performances in MLB are (all lefthanded hitters):
 Barry Bonds, 1.4217 (2004)
 Barry Bonds, 1.3807 (2002)
 Babe Ruth, 1.3791 (1920)
 Barry Bonds, 1.3785 (2001)
 Babe Ruth, 1.3586 (1921)
 Babe Ruth, 1.3089 (1923)
 Ted Williams, 1.2875 (1941)
 Barry Bonds, 1.2778 (2003)
 Babe Ruth, 1.2582 (1927)
 Ted Williams, 1.2566 (1957)
The highest singleseason mark for a righthanded hitter was 1.2449 by Rogers Hornsby in (1925), (13th on the alltime list). Since 1925, the highest singleseason OPS for a righthander is 1.2224 by Mark McGwire in (1998), which is good for 16th alltime.
Source: BaseballReference.com  SingleSeason Records for OPS
Adjusted OPS (OPS+)
OPS+, Adjusted OPS, is a closely related statistic. OPS+ is OPS adjusted for the park and the league in which the player played, but not for fielding position. An OPS+ of 100 is defined to be the league average. An OPS+ of 150 or more is excellent and 125 very good, while an OPS+ of 75 or below is poor.
The basic equation for OPS+ is
OPS+ = 100 * (\frac{OBP} {*lgOBP} + \frac{SLG} {*lgSLG}  1)
where *lgOBP is the park adjusted OBP of the league (not counting pitchers hitting) and *lgSLG is the park adjusted SLG of the league.
A common misconception is that OPS+ closely matches the ratio of a player's OPS to that of the league. In fact, due to the additive nature of the two components in OPS+, a player with an OBP and SLG both 50% better than league average in those metrics will have an OPS+ of 200 (twice the league average OPS+) while still having an OPS that is only 50% better than the average OPS of the league. It would be a better (although not exact) approximation to say that a player with an OPS+ of 150 produces 50% more runs, in a given set of plate appearances, as a player with an OPS+ of 100.
Leaders in OPS+
Through the end of the 2014 season, the career leaders in OPS+ (minimum 3,000 plate appearances) were
1. Babe Ruth, 206
2. Ted Williams, 190
3. Barry Bonds, 181
4. Lou Gehrig, 178
5. Rogers Hornsby, 175
6. Mickey Mantle, 172
7. Dan Brouthers, 170
8. Joe Jackson, 169
9. Ty Cobb, 168
10. Pete Browning, Jimmie Foxx & Mark McGwire, 163
Source: BaseballReference.com  Career Leaders & Records for Adjusted OPS+.
The only purely righthanded batters to appear on this list are Hornsby, Foxx, and McGwire. Mantle is the only switchhitter in the group.
The highest singleseason performances were:
 Barry Bonds, 268 (2002)
 Barry Bonds, 263 (2004)
 Barry Bonds, 259 (2001)
 Fred Dunlap, 258 (1884) *
 Babe Ruth, 256 (1920)
 Babe Ruth, 239 (1921)
 Babe Ruth, 239 (1923)
 Ted Williams, 235 (1941)
 Ted Williams, 233 (1957)
 Ross Barnes, 231 (1876) **
 Barry Bonds, 231 (2003)
Source: BaseballReference.com  SingleSeason Leaders & Records for Adjusted OPS+
*  Fred Dunlap's historic 1884 season came in the Union Association, which some baseball experts consider not to be a true major league
**  Ross Barnes may have been aided by a rule that made a bunt fair if it first rolled in fair territory. He did not play nearly so well when this rule was removed, although injuries may have been mostly to blame, as his fielding statistics similarly declined.
If Dunlap's and Barnes' seasons were to be eliminated from the list, two other Ruth seasons (1926 and 1927) would be on the list. This would also eliminate the only righthanded batter in the list, Barnes.
See also
Notes
 ^ See www.baseballprospectus.com or rec.sport.baseball.
 ^ Lewis, Michael. Moneyball: The Art of Winning an Unfair Game, 2003.
 ^ http://www.baseballreference.com/leagues/MLB/2008standardbatting.shtml
 ^ James, Bill. The 96 Families of Hitters. The Bill James Gold Mine, 2009, p.24.
 ^ John Thorn and Pete Palmer, The Hidden Game of Baseball, pp. 6970.
 ^ Alan Schwarz, The Numbers Game, pp. 165, 233.
References
