Slugging percentage calculator

How to use the slugging percentage calculator

1. Choose whether you have the number of singles or only total hits. Many box scores list hits, doubles, triples and home runs but not singles; the calculator works them out for you.
2. Enter at-bats and each type of hit. Empty boxes count as zero.
3. Read slugging percentage, total bases, batting average and isolated power, plus the total-bases sum so you can check it.

The slugging formula

TB = 1B + 2×2B + 3×3B + 4×HR

SLG = TB ÷ AB

Slugging percentage weights every hit by the bases it gives: one for a single, two for a double, three for a triple and four for a home run. Dividing those total bases by at-bats gives the average number of bases per at-bat. Batting average treats a home run like a single; slugging does not, which is why it is the usual measure of a hitter's power.

Only at-bats are in the denominator. Walks, hit by pitch, sacrifice bunts and sacrifice flies do not count as at-bats, so they leave slugging unchanged.

Isolated power (ISO)

ISO = SLG − AVG = (2B + 2×3B + 3×HR) ÷ AB

Isolated power removes the singles from the picture. Subtracting batting average from slugging leaves only the extra bases from doubles, triples and home runs. Two hitters can both slug .450; the one with the lower batting average and higher ISO gets more of his value from power.

Worked example

The numbers already in the tool: 100 singles, 25 doubles, 2 triples and 20 home runs in 500 at-bats.

1. Total bases = 100 + 2×25 + 3×2 + 4×20 = 100 + 50 + 6 + 80 = 236.
2. SLG = 236 ÷ 500 = .472.
3. Hits = 100 + 25 + 2 + 20 = 147, so AVG = 147 ÷ 500 = .294.
4. ISO = .472 − .294 = .178, which matches (25 + 2×2 + 3×20) ÷ 500 = 89 ÷ 500.

Switch to Total hits mode and enter 147 hits with the same doubles, triples and home runs: you get the same .472, because the calculator finds 100 singles itself.

Same at-bats, very different hitters

Two hitters with 500 at-bats each show why slugging matters:

Hitter A has the better batting average, but Hitter B reaches 75 more bases. That is the gap that slugging and isolated power reveal and batting average hides.

Tips

• If the tool says extra-base hits are more than hits, a home run has probably been counted twice: total hits already include doubles, triples and home runs.
• Softball, college and youth leagues use exactly the same formula. Only the typical values differ with field size and pitching, so compare hitters within the same league and season, never across levels.
• Small samples swing hard: one home run in 10 at-bats adds .400 of slugging for that stretch.
• Add on-base skills with the OPS calculator, check hits alone with the batting average calculator, and for pitchers use the ERA calculator.

How we tested it

The formulas run against automated Node tests with the worked example above: 100 singles, 25 doubles, 2 triples and 20 home runs in 500 at-bats give 236 total bases, a .472 slugging percentage, a .294 batting average and a .178 ISO. A further test enters the same line as 147 total hits and checks the slugging is still .472. The OPS tests also check slugging of 261 total bases in 520 at-bats (.502).