How To Use

What this app does

JonRon Model predicts the probability that an MLB batter will hit a home run in today's game using a v4 stacked ensemble of 4 machine learning algorithms trained on 301,440 plate appearances. It compares those probabilities against sportsbook odds to identify bets with positive expected value (+EV), and provides pitch-level matchup analysis so you can verify the edge before betting.

Home Run Probabilities

The main page shows every batter-pitcher matchup for today's slate, ranked by home run probability. Here's what each column means:

HR %The model's predicted probability this batter hits 1+ HR today. Calibrated so 5% means roughly 5 in 100 predictions hit.
OddsBest available sportsbook odds across FanDuel, DraftKings, BetRivers, Caesars, and others. Shows which book has the best line.
ImpliedThe sportsbook's implied probability from their odds. Compare to HR % to spot edges.
+EVExpected value edge. Positive = model sees an edge over the book. Higher = stronger bet.
WxGame-time weather. Green = warm/wind out (favorable). Yellow = neutral. Red = cold/wind in. Hover for exact temp and wind.
UnitsRecommended bet size using quarter-Kelly criterion. 1u = 1% of your bankroll.
InsightPitch-specific matchup narrative explaining why the model likes (or doesn't like) this matchup.

Tip: Use "Show +EV only" to filter to just the bets with an edge. Sort by +EV to find the strongest edges. Filter by team logo to focus on a specific game.

Barrel Edge

This tab ranks batters by their barrel rate against the specific pitches they'll face today. Unlike the aggregate HR probability, Barrel Edge shows you the raw contact quality data behind each matchup.

Barrel RtWeighted barrel rate across the pitcher's top 2-3 pitch types, weighted by usage. Higher = batter crushes what this pitcher throws most.
Pitch pillsGreen-highlighted pitches are "vulnerable" (pitcher allows high barrel% or fly ball% on that pitch). Gray pitches are neutral.
L10/L15/L25Controls how many recent batted ball events per pitch type are used. L25 is the most stable. L10 captures hot streaks but is noisier.
Green borderLeft border brightness indicates barrel edge tier. Bright green = top tier (25%+). Faded = lower tier.
* Low sampleUnder 10 batted balls against that pitch type. Shown for reference but excluded from the weighted barrel calculation.

How to use it: A batter ranked #15 in HR probability but #1 in Barrel Edge is someone the aggregate model may undervalue. If they barrel 30%+ of the pitcher's primary fastball thrown 50% of the time, that's a strong signal. Click any row to expand per-pitch detail with barrel%, FB%, exit velo, hard hit%, pitcher barrel allowed, sample size, and date range.

Placing bets

Click the "Bet" button on any prediction to open the bet modal. As you type in your odds, the modal calculates your expected value in real time, so you can instantly see if a line is still +EV at your book's price.

Live EVThe green/red EV display updates as you change the odds field. Green = edge exists at this price. Red = book has it priced correctly.
UnitsDefault is 0.5u. Increase for stronger edges. The model uses quarter-Kelly: even a big edge gets conservative sizing.
BookSelect your sportsbook so you can track which books give you the best lines over time.

Matchup detail page

Click any batter on the daily board to open the full matchup breakdown. This is where you do due diligence before placing a bet.

Rolling performance shows recent form across L5, L10, L15, L20 games and season. Look for batters trending up in ISO, barrel rate, and exit velocity.
Pitch matchup matrix shows pitcher vulnerability and batter performance by pitch type. Edge grades (A+ through F) combine both sides. Click any pitch row to expand the full scouting card.
Batted balls show recent contact quality. Green borders = HR-quality contact. Even field outs with 95+ mph exit velo and 25-35 degree launch angle are positive signals.
Environment edge shows wind, temperature, air density, and park effects for this specific game.

What makes a strong HR bet

Pitcher's primary pitch is hittable. High usage fastball with high ISO allowed, high barrel rate, and low IVB. Low IVB means the pitch doesn't "rise," making it easier to drive.
Batter barrels that pitch type. Check the Barrel Edge tab. 10%+ barrel rate on a high-usage pitch is the strongest single signal. Confirm with the batted ball data on the detail page.
Environment helps. Warm weather (75F+), wind blowing out, hitter-friendly park. The Wx column shows this at a glance.
Odds offer value. Look for +5% EV or higher. The bet modal shows live EV as you enter your odds.

Red flags

Elite breaking stuff. High IVB (17+ inches) on fastball and heavy break on slider/curve. Hard to elevate.
Low barrel rate on primary pitch. If the Barrel Edge shows 0% barrel rate with 20+ BBs against the pitcher's main pitch, the batter can't touch it.
Cold weather + wind in. Suppresses fly ball carry by 10-15 feet. Wx column shows red.

v4 Model (2026 Season)

The current model is a stacked ensemble of XGBoost (Tweedie loss), LightGBM, CatBoost, and EBM (Explainable Boosting Machine) trained on 301,440 plate appearances from 2024-2025 with 68 features.

New in v4: Pitch-mix weighted features account for how a batter performs against the specific pitches a pitcher actually throws, not just aggregate stats. This catches matchups where a batter's overall numbers look good but they struggle against the pitcher's primary arsenal.

Calibration: Probabilities are calibrated so that when the model says 5%, roughly 5% of those predictions result in a HR. A 10% per-plate-appearance cap prevents physically impossible game-level probabilities. The highest single-game probability is capped around 40%, which represents an elite hitter in an ideal matchup with 4-5 plate appearances.

Weather: Every prediction includes game-time temperature, wind direction, and air density. Coverage is near 100% for all MLB parks.

Top features: Platoon advantage, batter total PA, hard hit rate, pitcher velocity, launch angle, park HR factor, pull rate, and pitch-mix weighted ISO are the most predictive features in the model.

Performance tracker

Tracks your betting results and the model's overall prediction accuracy.

Model performance shows hit rates by probability tier and +EV range across ALL predictions, not just your bets. This validates the model is calibrated.

Your bet performance tracks W-L, net units, and ROI on bets you've actually placed. Each bet shows the EV at the time you placed it.

Expect variance. You need 200+ bets before results are statistically distinguishable from luck. Focus on process (betting +EV spots) not outcomes.

Same-Game Parlays

Build custom HR parlays by searching players and adding them to your slip. The builder shows combined probability, fair odds, and whether the book's parlay price offers +EV. Model-generated parlays surface the highest-probability and highest-EV combinations automatically. Note that books apply correlation adjustments to SGP pricing, so model fair odds assume independent events.

Bullpen Rankings

All 30 teams ranked by bullpen HR vulnerability using a composite score of barrel rate, fly ball%, hard hit%, HR/9, and inverse whiff%. High-vulnerability bullpens are targets for late-game HR bets and same-game parlays. Sortable by any stat column. Hover any header for the stat definition.

Bankroll management

1 unit = 1% of your total bankroll. If you have $1,000, 1 unit is $10.

Most bets will be 0.5-1.5 units. The model uses quarter-Kelly criterion for conservative sizing.

Never chase losses. Home runs are rare events (3-4% of plate appearances). Even elite hitters go multiple games without one. This app gives you a mathematical edge, not certainty.

Important: Bet responsibly and within your means. A minimum bankroll of 100-200 units is recommended. Expect 500+ bets to confidently distinguish skill from variance.