Slugging Percentage Calculator (SLG) — Total Bases per At-Bat

Background.

Picture two hitters with 600 at-bats each. One collects 180 singles and nothing else, a .300 batting average. The other manages only 140 hits, a .233 average, but 20 of them are doubles and 40 are home runs. Batting average prefers the first hitter by a wide margin. Slugging percentage turns the order round, .300 for the singles hitter and .467 for the one who drives the ball, because it counts how many bases each hit was worth, not only whether it happened.

The definition is one clause of Official Baseball Rule 9.21(c): divide the total bases of all safe hits by the total times at bat. A single is worth one base, a double two, a triple three and a home run four. Nothing else adds to the total. A stolen base, a runner moving up on a wild pitch, a walk or an error contributes nothing, because total bases are earned only with hits.

The denominator is official at-bats, the same one batting average uses, so slugging takes no notice of walks, hit-by-pitches or sacrifices: they are neither hits nor at-bats, and they change neither the top nor the bottom of the fraction. That is a division of labour rather than an oversight. On-base percentage measures how often a hitter reaches base, slugging how much each hit is worth, and adding the two gives OPS.

The name misleads. Slugging percentage is not a percentage at all but total bases per at-bat, with a ceiling of 4.000 for a batter who homers every time up. A .500 slugging percentage means five bases for every ten at-bats. Major League Baseball as a whole has slugged close to .400 in recent seasons, and Barry Bonds's .863 in 2001 is the single-season record.

You enter the line as box scores and season tables print it: at-bats, hits, doubles, triples and home runs. Singles are found by subtraction, which avoids counting the extra-base hits twice.

What is slugging percentage calculator?

Slugging percentage (SLG) is total bases divided by official at-bats. Total bases weight each hit by the base the batter reached on it, one to four, and MLB's glossary is explicit that a player can add to that tally only through a hit. Baseball prints SLG to three decimal places with no leading zero, so 0.6462 appears as .646.

It always sits at or above batting average, because both share the same denominator and every hit is worth at least one base. The gap between them is isolated power (ISO), which MLB publishes in two equivalent forms: slugging minus batting average, or (doubles + 2 × triples + 3 × home runs) ÷ at-bats. ISO counts only the extra bases beyond first, so it isolates power from contact. A hitter of nothing but singles has an ISO of .000. Slugging's usual partner is on-base percentage, (H + BB + HBP) ÷ (AB + BB + HBP + SF); the sum of the two is OPS, the most quoted one-number summary of a hitter.

Slugging can be worked out for anyone who has batted: a single game, a season, a career, a team, or, from the other side, the batters a pitcher has faced, where it is called slugging percentage against. For the league leaderboard, Rule 9.22(a) sets the same qualifying standard as for the batting and on-base titles, 3.1 plate appearances per scheduled team game, which is 502 in a 162-game season.

How to use this calculator.

1. 01Enter official at-bats, the AB column of a season table, not plate appearances (PA), which is the larger figure. Walks, hit-by-pitches and sacrifice bunts and flies are already left out of AB, so do not subtract them again.
2. 02Enter total hits, including the extra-base hits. A season line that reads 197 H, 38 2B, 7 3B, 54 HR has 197 hits in all, of which 98 were singles.
3. 03Enter doubles, triples and home runs. If together they come to more than the hit total, the line is impossible and the calculator will stop and say so; hits also cannot exceed at-bats.
4. 04Check total bases against the source. Most season tables print a TB column, and the quick hand check is hits + doubles + 2 × triples + 3 × home runs.
5. 05Read slugging to three decimals, the way baseball prints it, then compare it with batting average and isolated power to see how much of the figure comes from power.

The formula.

Three steps get from a box-score line to the result. First, singles: 1B = H − 2B − 3B − HR, because the hit total already contains every double, triple and home run. Second, total bases: TB = 1B + 2 × 2B + 3 × 3B + 4 × HR. An equivalent form skips the singles step, TB = H + 2B + 2 × 3B + 3 × HR, since every hit is worth at least one base and each extra-base hit adds its surplus. Third, the rule: SLG = TB ÷ AB.

Batting average is H ÷ AB, and isolated power is the difference, SLG − AVG. Subtracting hits from total bases leaves exactly the extra bases, so ISO also equals (2B + 2 × 3B + 3 × HR) ÷ AB, and the two routes agree to the last digit.

All five inputs are counts, so they must be whole numbers. At-bats must be at least one, hits cannot exceed at-bats, and doubles, triples and home runs together cannot exceed hits, which would leave a negative number of singles.

The weights 1, 2, 3 and 4 measure distance round the bases, not runs. Run-value research, the linear weights behind statistics such as weighted on-base average, finds that a double is worth less than two singles in runs produced and a home run well under four, because much of a hit's value lies in not making an out and in moving runners already on base, which a single does nearly as well as a double. Slugging percentage therefore leans toward extra-base hits, home runs most of all. That is part of why it is usually read alongside on-base percentage rather than alone.

Because it is a ratio, every hitless at-bat lowers it. A single extra at-bat with no hit takes the 2024 line in the worked example from .6462 to .6452.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Office of the Commissioner of Baseball (2025). Official Baseball Rules, 2025 Edition, Rule 9.21(c): "Slugging percentage, divide the total bases of all safe hits by the total times at bat, as defined in Rule 9.02(a)". Rule 9.21(b) on the same page contains the explicit disambiguation from batting average — divide safe hits "(not the total bases on hits)" by at-bats.
2. [2]Office of the Commissioner of Baseball (2025). Official Baseball Rules, Rule 9.06 (Determining Value of Base Hits) and Rule 9.02(a)(8): the scorer scores each base hit as a one-base hit, two-base hit, three-base hit or home run, and reports "Total bases on safe hits" as its own column. Source of the 1/2/3/4 weighting. Rule 9.22(a) gives the 3.1-plate-appearance qualifying standard shared by the batting, slugging and on-base titles.
3. [3]Major League Baseball. Official MLB Glossary, "Total Bases (TB)": "A batter records one total base for a single, two total bases for a double, three total bases for a triple and four total bases for a home run… A player can only add to his total-bases tally through a hit. Advancing on the basepaths -- even via a steal -- has no impact on a player's total bases."
4. [4]Major League Baseball. Official MLB Glossary, "Slugging Percentage (SLG)": "Slugging percentage represents the total number of bases a player records per at-bat… the formula for slugging percentage is: (1B + 2Bx2 + 3Bx3 + HRx4)/AB", plus the note that it excludes walks and hit-by-pitches and can be applied to pitchers as slugging-percentage against.
5. [5]Major League Baseball. Official MLB Glossary, "Isolated Power (ISO)": "The formula (1x2B + 2x3B + 3xHR) / At-bats OR Slugging percentage - Batting average". Both forms are computed on this page and agree to ten decimal places.
6. [6]MLB Stats API (statsapi.mlb.com), season hitting statistics for player 660271 (Shohei Ohtani), 2024: 636 at-bats, 197 hits, 38 doubles, 7 triples, 54 home runs, totalBases 411, published slg ".646". Source of the worked example; the same endpoint for players 592450 and 677951 supplies two independent checks of this calculator.