Park factors quantify how much a ballpark inflates or suppresses runs vs league average. Coors Field at 1.23x means 23% more runs than average; Petco at 0.96x means 4% fewer. Here's why park factors are essential to any MLB total.
What Park Factor Means
A park factor is a multiplier. 1.00 = neutral (league average), 1.10 = +10% runs, 0.90 = -10% runs. The number reflects historical run-scoring rates at that ballpark normalized for opposing teams + weather + season.
What Drives Park Factors
Outfield dimensions, Coors Field has one of MLB's deepest outfields, and the ball carries farther, not shorter, in thin air.
Altitude, Coors at 5,200 ft has 17% thinner air, ball flies further. Ditto Chase Field (1,100 ft).
Foul territory, large foul territory (like Oakland's old Coliseum) catches more pop-ups, fewer extra-base hits, fewer runs.
Wind patterns, Wrigley Field's run factor swings wildly by wind direction. South or southwest wind (blowing out): hitter park. North or northeast wind off Lake Michigan (blowing in): pitcher park.
Marine layer, Oracle Park + Petco Park have dense marine air that cuts ball carry late afternoon onward.
Park Factor by Handedness
Most parks aren't symmetric, Yankee Stadium boosts LHB power (short right field) more than RHB. Fenway boosts RHB more (Green Monster). Our model uses HR-by-handedness park factors blended at 30% with the flat run factor, the flat factor captures the bulk run effect from singles/doubles/base advancement; the handedness-specific HR factor catches lineup-composition swings.
Top 5 Hitter Parks (most run-friendly)
Coors Field (1.23x), altitude, dry air
Great American Ball Park (1.10x), small dimensions, hot summers
Fenway Park (1.07x): Green Monster
Citizens Bank Park (1.06x): small dimensions, humid summer
Chase Field (1.05x), altitude + retractable roof
Top 5 Pitcher Parks (most run-suppressing)
loanDepot park (0.88x): retractable roof, climate-controlled
Oracle Park (0.90x), marine air, deep RF
T-Mobile Park (0.91x), cool marine air
Tropicana Field (0.93x), dome, dead air
Citi Field (0.95x), deep dimensions
How to Use Park Factors
If you bet a total without considering park factor, you're flying blind. A 9.0 OVER at Coors Field is not the same as a 9.0 OVER at Petco, the same offensive matchup produces ~2.5 more runs at Coors. Sharp totals bettors check the venue first, every time. Our per-ballpark pages show park factors + today's games at each stadium.
Apply This Today
Theory is one thing, using the concept on tonight's slate is the value. These hubs are the practical application: