Why models matter: finding and evaluating bets
How models and data automation help us evaluate thousands of bets, with research and judgment shaping each decision.
Fourth & Value · Learn
Understand the price before you bet.
Evergreen fundamentals: how sportsbooks set prices, what a bet really costs, and how to compare an opinion with the market. For dated game analysis, see the Blog.
Start here
Three reads, in order. Together they cover the core idea behind everything on this site: the price matters as much as the pick.
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Basics · 7 min
What is vig? How sportsbooks make money
What the vig is, why −110 on both sides adds up to 104.76%, what the book really keeps, and how to strip it out to get fair probabilities.
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Basics · 9 min
Synthetic hold: the true price of any betting market
Take the best price on each side across books and a 4.5% hold drops to about 3%. How to calculate it, and when it goes negative.
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Case study · 5 min
The edge was the price
A model disagreement shrank to almost nothing, while the same bet paid at one book and lost at another.
Guides
Concepts that don't expire with a game. Examples may come from a past slate; the idea still applies.
How we read Chris Sale’s pitcher-outs prop
Compare averages, hit rates, push protection and prices, then check the context before betting.
Same bet, different rules: how house rules decide what you’re betting
Overtime, shootouts, regulation-only lines and scratched players. Why matching rules comes before comparing prices.
NFL betting rules: overtime, ties and player props
Does overtime count, what a tie does to your moneyline, and when an injured player’s prop still stands.
MLB betting rules: rain, scratched pitchers and props
Rain-shortened games, action vs. listed pitchers, extra innings and the one-plate-appearance rule.
NBA betting rules: overtime, player props and the player who sits
Overtime in totals and props, half and quarter bets, and what happens when a player sits or leaves early.
NBA player props: minutes, rest and injury news
Why minutes move props more than matchups, how back-to-backs and the injury report work, and what happens when a star sits.
NBA 2026–27 preview: the markets and props we track
The summer’s biggest moves, the NBA markets on our board, and what books charge on props compared with game lines.
What is vig? How sportsbooks make money
Break-even rates, overround versus hold, and how to devig a price.
Synthetic hold: how to find the true price of any betting market
Best price on each side, fair odds from the whole market, arbitrage and its catches.
Sharp vs. soft sportsbooks: how Pinnacle shapes the odds
How markets are made, why sharp prices matter, and how to check your book’s price against a no-vig fair price.
The edge was the price
Why we shrink model projections toward the market, and why line shopping can matter more than the pick.
Opening lines vs. closing lines
Why sharp bettors bet early, what it costs them, closing line value and middles.
Structural arbitrage: when props contradict each other
Ratio screens, the low-volume trap, NBA combined props, and how to check a gap with probabilities.
Over receptions, under yards: why it isn’t arbitrage
Every outcome of the prop pair that looks free, the math, and what real arbitrage looks like.
Home field in player props: small for yards, bigger for touchdowns
Measured on 2012–2025 games: about 1.4% for yardage, about 5% for touchdowns, and why personal splits don’t predict.
Tools
Calculators that run in your browser. Nothing you enter is sent anywhere.
Synthetic Hold Calculator
Enter each book's price on both sides of the same line. See every book's hold, the best price per side, the synthetic hold, consensus fair odds and the stake split when a market goes negative.
Odds Calculator
Convert American and decimal odds to implied probability, remove the vig to get fair odds and hold, and check a bet’s break-even and expected value.
Closing Line Value Calculator
Compare your price with the closing line: the closing no-vig probability, your CLV in points and the return it implies.
Kalshi Odds Converter
Turn a Kalshi price in cents into American odds and a break-even win rate with the fee included, or find the Kalshi price that beats a sportsbook line.
Betting Basics videos
Short narrated explainers, about two minutes each.
Episode 01 · 1:18
Why winning half your bets can still lose money
The break-even point at −110, overround, and devigging.
Episode 02 · 1:46
Synthetic hold: the true price of any betting market
Building the best market across books, fair odds, and why a negative hold is rarely free money.