What this is

A tweakable home run probability board. Every batter facing a probable pitcher today gets a 0–100 HR Score and a fair-odds estimate. Slide the factor weights to match how you think about HRs — the board re-ranks live.

The factors

• Batter power — ISO and AB/HR pace this season.
• Batter contact quality — barrel%, hard-hit%, average exit velocity, launch angle sweet spot (12–25°).
• Starter vulnerability — HR/9, barrel% allowed, hard-hit% allowed.
• Bullpen vulnerability — opposing team's top-8 relievers by usage, weighted HR/9 + barrel% allowed.
• Park factor — handedness-aware HR park factor. Coors, Yankee Stadium short porch, etc.
• Weather — wind direction relative to center field, wind speed, temperature. Domes neutral.
• Platoon edge — L vs R / R vs L gets a bump. Same-hand gets a fade.
• Recent form — HR per PA over the last 15 games.
• Lineup spot — proxy for plate appearances (data permitting).

Compare to the book

Click any batter to expand. Paste the sportsbook's HR odds (e.g. +650) — the page tells you how many percentage points of edge the model thinks you have. Positive edge = you bet, negative = pass.

Data sources

• • MLB Stats API — schedule, rosters, season + game-log stats
• • Baseball Savant — barrel%, exit velo, hard-hit%
• • Open-Meteo — game-time wind + temp

All free, no API keys. Heavy in-memory cache so the board doesn't pound them.