Advanced Theory
intermediate10 min read
Expected Value (EV) Deep Dive: The Foundation of All Gambling Math
Every gambling decision comes down to one question: is this bet +EV or -EV? Here's how to calculate it for any situation.
What is Expected Value?
Expected Value (EV) is the average amount you expect to win or lose per bet if you made the same bet an infinite number of times. It's the single most important concept in gambling mathematics.
The Formula
EV = (Probability of Winning × Amount Won) - (Probability of Losing × Amount Lost)
Sports Betting EV
Example: Standard -110 Bet
- Risk: $110 to win $100
- If your true win probability is 53%:
- EV = (0.53 × $100) - (0.47 × $110) = $53 - $51.70 = +$1.30 per bet
Example: Underdog at +200
- Risk: $100 to win $200
- If true win probability is 38%:
- EV = (0.38 × $200) - (0.62 × $100) = $76 - $62 = +$14 per bet
Casino Game EV
Roulette (American, betting red)
- Win: $100 (probability: 18/38 = 47.37%)
- Lose: $100 (probability: 20/38 = 52.63%)
- EV = (0.4737 × $100) - (0.5263 × $100) = -$5.26 per $100 bet
Blackjack (basic strategy)
- EV ≈ -$0.50 per $100 bet (0.5% house edge)
Craps (pass line + 3-4-5x odds)
- EV ≈ -$0.37 per $100 total wagered
Lottery EV
Powerball ($2 ticket, $100M jackpot)
- Non-jackpot EV: $0.32
- Jackpot EV: $100M × (1/292M) = $0.34
- Total EV: $0.66
- EV per ticket: -$1.34
The Key Insight
Every gambling decision should be evaluated through the lens of EV:
- +EV bets make money long-term (even if they lose short-term)
- -EV bets lose money long-term (even if they win short-term)
- The goal is to find and exploit +EV opportunities
Why Short-Term Results Don't Matter
A +EV bet can lose. A -EV bet can win. Over 1 bet, anything can happen. Over 10,000 bets, results converge toward the expected value. This is the Law of Large Numbers, and it's why casinos always win — they play enough hands for the math to work.
Practical Applications
- Sports betting: Calculate EV before every bet. If it's not +EV, don't bet.
- Casino games: Know the house edge. You're paying for entertainment.
- Lottery: Understand you're buying a dream, not an investment.
- Poker: Every decision should maximize your EV.
