Home / Learn / What Is ISO (Isolated Power)?

What Is ISO (Isolated Power)?

ISO, short for Isolated Power, measures a hitter's raw power by counting only extra bases. It is calculated as slugging percentage minus batting average, which strips out singles and leaves just doubles, triples, and home runs. A higher ISO means more extra-base pop. Around .140 is league average, and .200 and up marks a premier slugger.

How ISO is calculated

The simplest way to find ISO is slugging percentage minus batting average (ISO = SLG - AVG). Because slugging counts total bases and batting average counts hits regardless of type, subtracting one from the other removes the value of singles and leaves only the extra bases. You can also build it directly from the box score: ISO = (doubles + 2 times triples + 3 times home runs) divided by at-bats. Both formulas give the same number, which represents the extra bases a hitter averages per at-bat.

An example makes it clear. A player who goes 4-for-10 with four singles has a .400 average and a .400 slugging, for an ISO of .000. A player who goes 1-for-10 with a single home run has a .100 average and a .400 slugging, for an ISO of .300. Same slugging, very different power, and ISO is the number that separates them.

What counts as a good ISO

ISO is scaled like batting average, so the numbers look familiar. Per the FanGraphs benchmarks, roughly .140 is league average, .170 is above average, .200 is great, and .250 is excellent. On the low end, around .100 is poor and .080 is well below replacement power. The league-average figure drifts year to year with the run environment, so read a hitter against the current season rather than a fixed line. The premier power threats in any given year live in the .250 and up range.

What ISO does and does not tell you

ISO is a pure power read, not a measure of overall value. It does not weigh a triple as worth more than a double the way wOBA does, and it is not park or league adjusted, so the same ISO is more impressive in a pitcher's park than in a hitter's haven. It also takes a large sample to stabilize: FanGraphs notes it takes roughly 550 plate appearances before a hitter's ISO becomes predictive of his future ISO. A two-week hot streak with a .350 ISO is noise, not a new skill level.

Why ISO matters for betting

ISO is a fast, reliable filter for power markets like home runs and total bases. Two hitters can carry the same batting average while one slaps singles and the other drives the ball, and ISO is the stat that flags which is which. A high, stable ISO points to the bats that actually produce extra bases, which is exactly what a home run or total-base prop needs. It works best read alongside the underlying contact quality, since raw power still needs the right launch angle, park, and matchup to clear the fence.

How BetLogic helps

BetLogic's HR Sheet leans on power signals like extra-base rate and barrel contact when ranking the day's home run plays, then layers in the pitcher matchup, ballpark, and weather. See today's home run picks, updated before first pitch. To see how ISO fits with the broader rate stats, read what OPS is, and for the contact quality underneath it, see what barrel rate is.

Frequently asked questions

How is ISO calculated?
The quick way is slugging percentage minus batting average (SLG - AVG). You can also compute it as (doubles + 2 times triples + 3 times home runs) divided by at-bats. Both give the extra bases a hitter averages per at-bat.
What is a good ISO in MLB?
Roughly .140 is league average. Above .170 is above average, .200 is great, and .250 or higher is excellent. Anything around .100 or below signals a lack of power. The league-average mark shifts year to year.
What is the difference between ISO and slugging percentage?
Slugging percentage counts total bases from all hits, including singles. ISO strips out singles by subtracting batting average, so it isolates only the extra-base power. Two players with the same slugging can have very different ISOs.
Why do bettors use ISO?
It is a clean, quick read on raw power, which drives home run and total-base props. A high, stable ISO flags hitters who produce extra bases rather than singles, though it works best alongside park, pitcher, and contact-quality data.

More from BetLogic Learn

What Is a Stolen Base Bet?Does a Walk Count as a Total Base in Betting?How to Bet MLB Home Run PropsWhat Is Exit Velocity in Baseball?Highest Exit Velocity in MLB HistoryWhat Makes the Best AI Sports Betting Tool?What Is Barrel Rate (and Why It Predicts Home Runs)?What Is a Strikeout Prop?What Is K% (Strikeout Rate)?What Is an H+R+RBI Prop?What Is Park Factor and How It Affects Home RunsWhat Is BvP (Batter vs Pitcher) and Does It Matter?What Is Catcher Pop Time?What Is Sprint Speed in MLB?What Are Expected Stats (xwOBA, xBA, xSLG)?Platoon Splits, Explained: How Lefty/Righty Matchups Move MLB PropsBatter vs Pitch Type: Why Arsenal Matchups Beat BvP for Prop BettingStatcast Stats for Betting: The Metrics That Actually Predict PropsWind, Heat, and Home Runs: How Weather Moves MLB HR PropsWhat Is Launch Angle in Baseball?What Is WHIP in Baseball?What Is OPS in Baseball?What Is Hard-Hit Rate in Baseball?What Is wOBA in Baseball?

BetLogic provides data-driven insights only and does not constitute financial or gambling advice. Please bet responsibly and only what you can afford to lose. You must be of legal betting age in your jurisdiction.