What is Slugging Percentage? Definition, Formula, and Example

What is slugging percentage?

Slugging percentage (abbreviated SLG) measures a hitter's per-at-bat power output. Unlike batting average, which treats every hit equally, SLG weights hits by the number of bases they produce: a single counts 1, a double 2, a triple 3, and a home run 4. The resulting figure — total bases divided by at-bats — captures not just how often a hitter gets a hit but how much damage each hit does. A .400 SLG sits near league average, .500 is solid-regular power, and .600 or higher is MVP territory. The all-time single-season record is Barry Bonds' .863 in 2001.

How slugging percentage is calculated

The formula:

SLG = (1B + 2 × 2B + 3 × 3B + 4 × HR) ÷ AB

Where 1B, 2B, 3B, and HR are singles, doubles, triples, and home runs, and AB is at-bats (plate appearances minus walks, hit-by-pitch, sacrifices, and reaches on interference). Walks and hit-by-pitch are excluded entirely — SLG only counts what happened on contact or on a ball over the wall. Because the maximum a single at-bat can produce is 4 (a home run), SLG is bounded between 0.000 and 4.000, though no qualified hitter has ever cracked even 1.000 across a full season.

Worked example: Aaron Judge's 2024 season

In 2024, Aaron Judge appeared in 158 games with 559 at-bats, collecting 180 hits — 85 singles, 36 doubles, 1 triple, and 58 home runs. Calculating his total bases:

85 + (2 × 36) + (3 × 1) + (4 × 58) = 85 + 72 + 3 + 232 = 392

Dividing by 559 at-bats: 392 ÷ 559 = .701. That .701 SLG led the American League by more than 70 points and was the highest qualified SLG since 2004. By comparison, league-average SLG in 2024 was approximately .399, putting Judge's mark 76% above league average on this metric alone.

Why slugging percentage matters

SLG is the "S" in OPS (on-base plus slugging) and the foundation of most modern offensive metrics. Front offices use it for several decisions:

• Power isolation: SLG minus batting average yields ISO, the cleanest single-number power measure (Judge's 2024 ISO: .379).
• Lineup construction: Teams stack high-SLG hitters in the 2-3-4 spots where extra-base hits do the most damage with runners on.
• Contract valuation: Power hitters with .500+ SLG profiles command premium free-agent contracts because extra-base hits drive run scoring more efficiently than singles.
• Fantasy and DFS: SLG correlates strongly with RBI and runs scored — the counting stats that decide most fantasy categories.

Limitations and common misconceptions

SLG is not a percentage despite the name. A percentage is a fraction of total chances, but SLG can theoretically reach 4.000. Treat it as a rate, not a percent.

SLG also ignores walks. A patient hitter with elite plate discipline — think Juan Soto — sees his value show up in OBP, not SLG. And it is a context-blind raw number: a .500 SLG at Coors Field is less impressive than a .500 SLG at Petco Park because of park effects.

Finally, SLG conflates contact and power. A hitter with a .280 BA and .500 SLG is reaching base on extra-base hits at a healthy rate; one with .220 BA and .500 SLG barely makes contact but mashes when he does. ISO separates the two cleanly.

Related terms

• OPS — combines SLG with on-base percentage for a single offensive number.
• OPS+ — park- and league-adjusted OPS where 100 is league average.
• ISO — isolated power, SLG minus batting average.
• wRC+ — comprehensive park-adjusted offense, more refined than OPS+.
• Barrel rate — Statcast measure of optimal exit velocity and launch angle combos that produce extra-base hits.

In Legends Deck: SLG is one of the primary inputs to a hitter card's Power rating, alongside underlying Statcast metrics like average exit velocity and barrel rate. A card built around a 2024-Judge profile gets max-tier extra-base hit probability against righties but draws intentional walks in late-game leverage spots — your AI manager will pitch around him with first base open just like the real league did.