● EXPLAINER · BY MARCDUCK

What is ISO (Isolated Power) in MLB Betting?

Published June 2, 2026 · Updated September 29, 2026

ISO (Isolated Power) measures a hitter's pure power output by stripping batting average out of slugging. The formula: ISO = SLG - AVG. Elite is .260+; league average is around .160. ISO is the cleanest single-stat power indicator.

What ISO Measures

Slugging Percentage counts total bases per at-bat. But slugging includes singles, which aren't extra-base power. ISO subtracts batting average from slugging, leaving only the EXTRA bases (doubles, triples, HRs) per AB. The formula: ISO = SLG - AVG equivalently ISO = (2B + 2×3B + 3×HR) / AB.

The result is pure power isolation. A hitter with .280 AVG and .500 SLG has .220 ISO. A hitter with .200 AVG and .500 SLG has .300 ISO: same slugging, more power, less contact.

How to Read ISO

.260+: elite power (top 5-10 hitters per season)
.220-.260: very good power
.180-.220: above average power
.140-.180: league average
.100-.140: below average
Below .100: singles-only hitter (rare)

Why ISO Matters for Betting

ISO is the cleanest predictor of HR rate, which matters for:

Over/under totals. Hitter-heavy lineups (high ISO) blow up totals when paired with weak HR-allowing pitchers in hitter parks.
YRFI (Yes Run First Inning). High-ISO top-3 hitters can plate a 1st-inning run with one swing.
HR props. ISO + park HR factor + pitcher HR/9 = HR probability estimate.

ISO vs SLG

SLG includes singles, so a slap hitter who never strikes out can have high SLG without much power. ISO isolates the power component. For evaluating REAL power threat, ISO is strictly better than SLG.

ISO by Park

ISO is highly park-dependent. Hitters at HR-friendly parks (Coors, Great American, Yankee Stadium, Citizens Bank) post inflated ISOs that don't travel to road games. Hitters at HR-suppressing parks (such as Oracle Park and PNC Park) post deflated ISOs at home but real power on the road. For predictive use, look at road ISO separately or use park-adjusted ISO from FanGraphs.

ISO vs Handedness

Most hitters have meaningful ISO splits vs LHP vs RHP. A LHB power hitter might post .280 ISO vs RHP but .150 ISO vs LHP. Lineup ISO vs the opposing starter's handedness is the predictive number for tonight's game, not season-overall ISO.

How Bookie Bullies Uses ISO

ISO is not an input in the current model, and the model does not compute a per-at-bat HR probability. Power enters only indirectly, through team wOBA split by the opposing starter's handedness and confirmed-lineup xwOBA. The first-inning (NRFI/YRFI) read multiplies pitcher, park, weather, umpire, defense and market-total factors, with its offense factor switched off.

Apply This Today

Theory is one thing, using the concept on tonight's slate is the value. These hubs are the practical application: