Baseball has always been a game of statistics. Tracking a player’s success comes down to averages, algorithms, and formulas to determine whether or not a player is performing at a major-league level. It is common practice for baseball fans to argue about batting averages, earned run averages, or a player’s wins above replacement.

While stats have always been ingrained into the game of baseball, they have evolved with the sport over its 100-year-plus history. Baseball’s statistics world is dense and deep, and it’s easy to find yourself confused. One stat that has become one of the most prominent in judging a player’s offensive production is on-base plus slugging (OPS). In order to understand OPS, you must first take a look at a few other types of stats, namely on-base percentage and slugging percentage.

## On-base percentage

One of baseball’s core statistics, a player’s on-base percentage (OBP), measures how often that player gets on base, whether it be through a hit, walk, or hit by pitch. If a player reaches base via an error, fielder’s choice, dropped third strike, obstruction, or catcher’s interference, it does not count toward their OBP.

This is the formula for OBP: with *H* being the number of hits, *BB *being the number of walks, *HBP *being the number of time hits by pitch, *AB *being the number of at-bats, and *SF *being the number of sacrifice flies.

OBP can be understood as how many times a player reaches base per plate appearance. Although it is called a percentage, it is most commonly presented in the form of an average, e.g., .328. OBP is different from another prominent stat, batting average, as OBP takes walks and hit-by-pitch into account while batting average is purely based on how often a player gets on base via a hit.

Players with the best OBP often bat first in the lineup unless they are power hitters, who usually bat third or fourth. The league average OBP has fluctuated over the years, but in recent years it has been in the .310-.320 range. The best OBP over a career belongs to Hall of Famer Ted Williams, whose average OBP was .482 over his 19-year career.

## Slugging percentage

A player’s slugging percentage (SLG) measure’s his productivity as a hitter. Unlike batting average, which only takes hits into account, SLG takes specific types of hit into account: singles, doubles, triples, and home runs. SLG gives more weight to extra-base hits (doubles, triples, and home runs). Walks, times hit by pitch, catcher’s interference and sacrifices are excluded from SLG, as they do not constitute an official at-bat. Like OBP, SLG isn’t presented as a true percentage but as a decimal, e.g., .681.

Here is the formula for SLG:

, with *1B *being the number of singles, *2B *being the number of doubles, *3B *being the number of triples, *HR *being the number of home runs, and *AB *being the number of at-bats. SLG is a useful stat to determine a hitter’s power because the formula gives more weight to extra base hits.

The average slugging percentage in MLB tends to hover around .400, with the best hitters in a season usually eclipsing .600. The best slugging percentage over a career belongs to the legendary Babe Ruth, who slugged .689 over his 22-year career.

## On-base plus slugging

Now that we understand OBP and SLG, OPS is simple. A player’s on-base plus slugging is determined by adding his OBP and SLG together, representing his ability to get on base and hit for power, two of the most important skills of a good hitter. Again, OPS is presented as a decimal, e.g., .847. OPS is not a percentage of any kind, so numbers can go above 1.000. Here is the simple formula:

Checking a player’s OPS is a quick way to determine his overall production as a hitter; a more complete hitter will have a noticeably higher OPS than a below-average one. The best hitters in Major League Baseball tend to have an OPS above .800, while truly elite hitters can eclipse 1.000.

The best OPS over the course of a career again belongs to Babe Ruth, who posted an eye-popping 1.163 over his career.

When watching baseball, OPS is a great stat to know if you want to get a quick idea of a hitter’s level of production. For many baseball fans, the more you understand baseball’s statistics, the more enjoyment you’ll be able to get out of the game.