Building a Sports Betting Model: A Step-by-Step Framework

Why Build a Model?

A betting model is a systematic way to estimate the true probability of outcomes. Instead of relying on gut feelings, you use data to make decisions. This is how professionals operate.

The Framework

Step 1: Choose Your Market

Start narrow. Don't try to model everything at once.

• Pick one sport
• Pick one bet type (moneyline, spread, total, or props)
• Pick one league

Step 2: Identify Key Variables

What factors predict the outcome? Examples for NFL:

• Offensive and defensive efficiency (DVOA, EPA)
• Turnover rates
• Home/away performance
• Rest days
• Weather
• Injuries

Step 3: Collect Data

Sources for historical data:

• Pro Football Reference, Basketball Reference
• ESPN, NFL.com stats pages
• Specialized APIs (paid and free)

Step 4: Build Your Model

Start simple:

Power Rating Model:

1. Assign each team a rating based on performance metrics
2. The difference in ratings predicts the spread
3. Compare your predicted spread to the market

Example:

• Chiefs rating: +5.2
• Eagles rating: +2.1
• Home field advantage: +2.5
• Predicted spread: Chiefs -5.6
• Market spread: Chiefs -3.5
• Your model sees value on Chiefs -3.5

Step 5: Backtest

Test your model against historical data:

• Would it have been profitable?
• What's the sample size?
• Is the edge consistent across seasons?

Step 6: Track Live Performance

• Paper trade first (track without real money)
• Compare your predictions to closing lines
• Measure CLV over 500+ predictions

Common Mistakes

1. Overfitting — Making your model too complex to fit historical data perfectly. It won't work on future data.
2. Ignoring the market — The market is smart. If your model disagrees by 10+ points, your model is probably wrong.
3. Small sample sizes — Don't trust results from fewer than 200 predictions.
4. Not accounting for vig — Your model needs to beat the spread AND the juice.

Realistic Expectations

• A good model might find 2-5% edge on select games
• You won't have a bet on every game — maybe 20-30% of games offer value
• Expect 52-56% win rate on spread bets
• Profitability requires discipline and patience