When Parlays Are +EV (and When They Are Not)

How parlay payouts work

A parlay multiplies the decimal odds of every leg. Two −110 legs (1.91 × 1.91 = 3.65) pay roughly +265 — and require both to hit. The combined implied probability falls fast, so the payout has to be big enough to make the math worthwhile.

Why most parlays are -EV

Two reasons. First, the book takes vig on every leg, so the compounded vig is the parlay tax. Second, casual parlay bettors add legs to chase a payout, not because every leg is +EV — the result is a negative-EV ticket dressed up as upside.

When parlays are +EV

Parlays become +EV when every leg passes the value test independently AND the legs are positively correlated (or at least uncorrelated). Correlated parlays — for example, a quarterback's passing yards prop combined with the team's total points — are explicitly +EV when the model has both legs as edges.

Sizing parlays

Even a +EV parlay has higher variance per dollar than the underlying legs. Size at half Kelly or quarter Kelly. Never put a 'normal' stake on a 6-leg parlay just because the payout looks fun — at quarter Kelly the right stake might be 0.3% of bankroll.

Common mistakes

• Adding a -110 favorite as a 'lock' to boost the payout — you just added vig and lost EV.
• Stacking 5+ legs without checking the implied combined probability against your true model.
• Sizing the parlay like a single bet — variance compounds, sizing has to come down.

NotaSportsGuru's Parlay of the Day is a 2-leg combination, both legs ranked +EV by the model and chosen with mild correlation. The audited ledger shows the win/loss record at the exact combined odds posted that morning.