Original editorial illustration.
OPS adds on-base and slugging into one number. Learn MLB’s official formula, quick examples, common mistakes, and what to watch during games.
The quick answer
OPS is a single number that adds a hitter’s on-base percentage (OBP) and slugging percentage (SLG) to summarize how often he gets on base and how much damage he does when he hits.
Major League Baseball (MLB) defines OPS as OBP + SLG in its official Glossary, and the same concept can be applied to pitchers as “OPS against.” This explainer uses MLB Glossary definitions current for the 2026 MLB season.
The math, in plain English (MLB definitions)
- OPS = OBP + SLG, per MLB’s Glossary.
- OBP measures how frequently a batter reaches base: OBP = (H + BB + HBP) / (AB + BB + HBP + SF). Sacrifice bunts are excluded from the equation entirely, and reaching on error, fielder’s choice, or a dropped third strike does not count as “on base.”
- SLG captures power by valuing total bases per at-bat: SLG = TB / AB, where TB = 1B + 2×2B + 3×3B + 4×HR. Walks and hit-by-pitches do not enter SLG.
Two quick examples of calculating OPS
Example 1 (hypothetical, small sample): A batter has 4 plate appearances: single, double, walk, groundout. He has 3 at-bats (walks don’t count as AB) and 2 hits for 3 total bases.
OBP = (2 H + 1 BB + 0 HBP) / (3 AB + 1 BB + 0 HBP + 0 SF) = 3/4 = .750. SLG = 3 TB / 3 AB = 1.000. OPS = 1.750. That’s excellent, but it’s just one game.
Example 2 (hypothetical): Five plate appearances: single, hit-by-pitch, sacrifice fly, and two outs. At-bats = 3 (SF and HBP aren’t AB). Total bases = 1.
OBP = (1 + 0 + 1) / (3 + 0 + 1 + 1) = 2/5 = .400. SLG = 1/3 ≈ .333. OPS ≈ .733. Note how the sac fly increases OBP’s denominator, while the sac bunt (if it happened) would be excluded from OBP entirely and wouldn’t change SLG either.
What OPS tells you: and what it misses
OPS is useful because it combines getting on base (which sustains innings) with power (which advances runners and scores them). It’s a fast way to compare hitters within the same MLB season or ballpark.
But OPS gives OBP and SLG equal weight just by adding them. Many run-value studies show reaching base carries slightly more value than the same change in slugging, which is why MLB’s Glossary highlights alternative measures such as wOBA that weight events by their impact on scoring.
Context also matters. Ballparks and league run environments differ. MLB’s OPS+ adjusts OPS for park and league so 100 is average and numbers above/below reflect how a player compares in that setting. Use OPS for a quick scan; use OPS+ (or wOBA) when you want context and weighting.
What to watch during a game
Walks and hit-by-pitches raise OBP without touching SLG. In a hypothetical four-appearance game with two walks and two outs, the hitter has a .500 OBP and .000 SLG for that game. Whether the season OPS rises depends on the hitter’s earlier totals.
Singles raise both OBP and SLG, but extra-base hits move SLG a lot more. A double adds one hit to OBP’s numerator but two total bases to SLG’s numerator.
Sacrifice flies increase the OBP denominator (they’re included there) but are not at-bats, so they leave SLG’s denominator alone. Sacrifice bunts are excluded from OBP and are not at-bats, so a pure sac bunt typically doesn’t change OPS.
Reaching on error isn’t credited as a time on base in OBP and usually counts as an at-bat, which can pull both OBP and SLG down.
Common mix-ups to avoid
OPS is not the “slash line.” The slash line is AVG/OBP/SLG; OPS is just OBP + SLG.
OPS is not park- or era-adjusted. For cross-era or ballpark comparisons, look to MLB’s OPS+.
OPS isn’t a complete picture of offense. It excludes baserunning, double-play avoidance, and quality-of-contact nuance. Other measures can help answer separate questions about contact quality and the value of different outcomes. No single batting statistic covers everything a player contributes.
Small samples can wildly swing OPS. Over a week, two homers and a few walks can look like a breakout; over six months, the number stabilizes. Use OPS as a quick, MLB-defined snapshot, then dig deeper with supporting metrics where needed.