A single bet combining multiple selections — all must win for the parlay to pay out.
A parlay (called an accumulator in the UK) combines two or more individual bets into one. All selections must win for the parlay to pay out. The odds multiply together, creating larger potential payouts but lower win probability.
Parlays are the sportsbook's most profitable product because the vig compounds with each leg. A 4-leg parlay at -110 each has roughly 18% combined vig, compared to 4.5% on a single bet.
Correlated parlays (legs whose outcomes are related) can occasionally offer value, but standard parlays are mathematically disadvantageous.
parlayDecimalOdds = leg1 × leg2 × ... × legN impliedProb = 1 / parlayDecimalOdds
3-leg parlay at -110 each: 1.909 × 1.909 × 1.909 = 6.966. A $10 bet pays $69.66. True probability ≈ 12.5%, implied probability from fair odds = 14.4%.
The bookmaker's built-in commission. The difference between true odds and what you're offered.
Expected Value (EV)The average profit or loss per bet if you made the same wager thousands of times. Positive EV means long-term profit.
Implied ProbabilityThe probability of an outcome implied by the odds. Includes the bookmaker's margin (vig).