Find your SLG, see where your bases come from, preview your next at-bat, and plan the bases you need to hit a target.
Pick a mode. Blank hit boxes count as zero.
Walks and hit-by-pitch are not at-bats. Leave them out.
Add hits if you want batting average and isolated power too.
Type the target like .420 or 0.420. The planner tells you how many bases you need.
This calculator does more than divide two numbers. It gives you your slugging percentage, shows where your bases come from, tells you how your next at-bat will move the number, and plans the bases you need to reach a target.
Not sure where to start? Tap one of the three example hitters. All three bat .300, yet their slugging is very different. That gap is the whole reason this stat exists.
Slugging percentage, or SLG, measures how many bases a hitter earns per at-bat. The formula is simple: SLG = Total Bases ÷ At-Bats. A hitter with 140 total bases in 400 at-bats has a slugging percentage of .350.
Think of it as batting average with the right weights. Batting average gives a single and a home run one point each. Slugging gives them one base and four bases. The highest possible SLG is 4.000, which would mean a home run in every at-bat. It is written without a leading zero, so you say "three-fifty" for .350.
Total bases only count bases earned by hitting the ball safely. Here is how every common result is treated:
| Result | Total bases | Counts as an at-bat? |
|---|---|---|
| Single | 1 | Yes |
| Double | 2 | Yes |
| Triple | 3 | Yes |
| Home run | 4 | Yes |
| Out, strikeout, error, fielder's choice | 0 | Yes |
| Walk or hit-by-pitch | 0 | No |
| Sacrifice fly or bunt | 0 | No |
Here is a quick example. A hitter has 90 singles, 30 doubles and 10 home runs. Total bases are 90 + 60 + 40 = 190. Stolen bases never count, and neither do bases taken on an error or a throw. A reach on error is still an at-bat, so it adds 1 to the bottom of the fraction and nothing to the top.
In recent MLB seasons, the league average has sat around .400 to .415. Use these bands as a guide for pro baseball:
For perspective, Barry Bonds slugged .863 in 2001, the single-season record. Babe Ruth holds the career mark at .690, ahead of Ted Williams at .634 and Lou Gehrig at .632.
Amateur numbers run differently. Younger players often hit more singles and fewer homers, but errors and weaker defense can also push totals up. That is why the calculator has a level setting. Treat every scale as a rough guide, not a rule.
The best way to see why SLG matters is to compare three hitters. Each one has 500 at-bats and 150 hits. Each one bats exactly .300.
Same average, three very different players. The power hitter creates far more damage for the same number of hits. Batting average hides that. Slugging shows it. You can check your own average with the batting average calculator.
ISO, or isolated power, is simply SLG minus batting average. It removes singles from the picture and shows only the extra bases a hitter creates. Around .150 is typical in the majors. An ISO of .200 or more is real power. Under .090 usually means a contact and singles type.
ISO also explains how two hitters can slug the same. A .320 hitter with .130 ISO and a .250 hitter with .200 ISO both finish at .450. One does it with a high average, the other with power. When you scout a hitter, ask which path they take. This calculator shows ISO whenever it has hits.
After you calculate by hit type, the result shows a colored bar called "Where your bases come from." It splits your total bases into singles, doubles, triples and home runs. Two hitters with the same SLG can have very different bars.
A bar that is mostly light green means a singles-driven hitter. Slugging comes from volume, so it depends on a high average. A bar with a big dark green block means home runs carry the load. That hitter is streakier, since home runs come and go. A balanced bar with plenty of doubles often belongs to a gap hitter, who tends to age well and stay steady through slumps. The power profile tag under the bar sums this up using ISO.
Say a high school junior has 120 at-bats, with 36 hits: 24 singles, 8 doubles, 1 triple and 3 home runs. Total bases are 24 + 16 + 3 + 12 = 55. SLG is 55 ÷ 120 = .458. The average is .300, so ISO is .158, which is solid power.
On the high school scale that is a good number, not elite. The next at-bat table shows why it is hard to move quickly: one home run lifts it only to about .488. To reach .500 by the end of the season, the planner shows how many more bases the player needs. That is the kind of goal a coach can actually track.
SLG is useful, but it has blind spots you should know about.
Below your result, the calculator shows what happens to your SLG after one more at-bat. It tests an out, a single, a double, a triple and a home run, and shows the new SLG and the change for each.
The table teaches a useful lesson. Early in the season, one swing moves the number a lot. After 500 at-bats, even a home run barely changes it. It also shows that a single lifts SLG for almost every hitter, because one base is more than any normal SLG. An out always pulls it down. A walk or hit-by-pitch changes nothing at all.
Planner mode answers a question most calculators skip: how many bases do I still need? Enter your at-bats and total bases so far, your target SLG, and the at-bats left.
Take a hitter at .380 after 200 at-bats. That is 76 total bases. The goal is .420 with 100 at-bats left. The final season total will be 300 at-bats, so the hitter needs 126 bases in total. That means 50 more bases, or a .500 pace over the rest of the way.
The planner then checks if that pace is realistic compared with your current SLG. It also turns the answer into plain terms, such as singles, doubles or home runs. If the target is out of reach, it says so. If you are already safe, it shows your worst-case finish.
If you coach youth players, keep this simple. Teach good contact and a solid swing first. Power follows as kids grow.
The formula never changes, but the numbers do. In youth ball, defenses make more mistakes, so a ball in the gap can turn into extra bases more often. In high school, a .450 SLG is a strong season for most players. In college, the bat and the pitching get better, and a .500 SLG is a solid mark for a regular.
Softball players get the same stat with a shorter field and a larger ball, so doubles and triples are common and home runs are rarer. Use the level setting to get a fair rating. Compare a player to teammates and opponents in the same league, not to MLB.
Slugging is one piece of the picture. Use the batting average calculator for contact, the OPS calculator to combine on-base and power, and browse every tool on the tools page.
Can slugging percentage be higher than 1.000?
Yes. The maximum is 4.000. Over a full season it almost never happens, since Bonds' record is .863. Over a few games, a hot streak can easily go above 1.000.
Do walks count in slugging percentage?
No. Walks and hit-by-pitch are not at-bats and add no bases, so they leave SLG unchanged.
What is the difference between total bases and SLG?
Total bases is a count. SLG is that count divided by at-bats, so it is a rate.
What is the difference between SLG and OPS?
SLG measures power only. OPS adds on-base percentage to it, so OPS covers both.
Does reaching on an error count?
It counts as an at-bat with zero bases, so it lowers SLG slightly, just like an out.
Can I use this for softball?
Yes. SLG works the same in softball. Choose the youth or high school level for a fitting rating scale.