Understand Expected Value to Evaluate Any Bet
The casino publishes that price implicitly in its rules. Multiply each outcome by its probability and add the results to uncover the wager's cost.
Every gambling decision comes down to one number: expected value. Learn to compute it and you can evaluate any bet — casino, sportsbook, or a coin flip with a friend — without anyone’s opinion.
What expected value is
Expected value (EV) is the average result of a bet if you could repeat it forever. Multiply each outcome by its probability, add them up, and you have the long-run price of the wager.
Take a single-number bet in double-zero roulette. You win 35-to-1, but there are 38 pockets:
- Win: (1/38) × 35 = +0.921 units
- Lose: (37/38) × 1 = −0.974 units
EV = 0.921 − 0.974 = −0.053 units per unit bet, or −5.3%. Every $100 you put on a number costs you $5.26 on average. Not sometimes. On average, always.
The ten-second method
For any casino bet:
- List every outcome and its true probability.
- Multiply each payout by its probability.
- Subtract what you risked times the probability of losing it.
If the answer is negative — and in a casino it always is — that percentage is the house edge. The house doesn’t need luck; it needs volume.
Why negative EV games still fill casinos
Variance. Over a hundred spins, anything can happen, and that short-term noise is exactly what you’re buying: the possibility of walking away up. There’s nothing wrong with paying for entertainment. The mistake is believing a streak, a system, or a “due” number changes the underlying arithmetic. It never does — each spin resolves to the same −5.3%.
What you can actually control
You can’t make a casino bet positive-EV, but you can choose how much edge you give away:
- Game selection. House edge ranges from under 0.5% (blackjack with correct play) to over 15% (keno, some side bets). See our ranking of which games give you the best shot.
- Bet selection within a game. In craps, the pass line gives up 1.41% while the “any 7” bet gives up 16.7% — same table, twelve times the price.
- Speed. EV loss compounds per bet. Half the hands per hour is half the expected cost.
- Bankroll rules. Decide your loss limit before you play. EV tells you the average; variance guarantees the worst sessions will be much worse.
The takeaway
Expected value strips gambling of mythology. Every bet has a precise long-run price; the casino publishes it implicitly in the rules. Know the price, decide if the entertainment is worth it, and never pay more edge than you have to.