Expected Value Betting Explained
Expected value (EV) is the average dollar return per dollar staked if you repeated the same bet under the same odds and the same true probability forever. It is the single number that separates profitable bettors from gamblers.
The EV formula
EV per $1 staked = (win probability × (decimal odds − 1)) − ((1 − win probability) × 1). Multiply by stake to get dollar EV. A +5% EV on a $100 bet is +$5 in expectation; a −5% EV is −$5. Over thousands of bets the expected number is exactly what you get, up to variance.
EV vs win rate
Win rate without price is meaningless. A 60% win rate on −200 favorites is a losing strategy (break-even is 66.7%). A 45% win rate on +130 underdogs is winning (break-even is 43.5%). Always weigh win rate by the average price of the bets that produced it.
Why a +EV bettor can lose for weeks
EV is a long-run number. A 3% EV strategy on 1,000 bets has expected profit but real variance — drawdowns of 5–10 units are routine and 20-unit drawdowns happen. The bettor's job is to size correctly (Kelly or a fraction of it), keep volume up, and ignore the short-term scoreboard.
Where the model wins
Books need to price thousands of markets per day. They cannot price every player prop perfectly, especially on second-tier names where public attention is thinner. A model that grinds those markets, finds 3–6% edges, and bets the +EV ones with consistent sizing produces a real long-run return.
Common mistakes
- Anchoring on yesterday's results instead of the projected edge.
- Skipping bets because the edge feels small — small edges at scale beat big edges with hesitation.
- Sizing flat across bets with very different EV — Kelly says bet more when you have more edge.
NotaSportsGuru picks every leg by the same rule: model probability minus implied probability must be positive. The slate is ranked by edge, the Parlay of the Day takes the two highest combined-EV legs.
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Related guides
Value betting is placing wagers only when your estimated win probability is higher than the sportsbook's implied probability. The complete US bettor's guide.
How professional bettors size every wager: bankroll definition, flat stakes vs Kelly, when to rebalance, and the math behind staying in the game.
Closing line value is the leading indicator of long-run sports-betting profit. How to track CLV, why it matters more than win rate, and how to beat the close.
Glossary references
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