If you read nothing else on this site, read this. Parlays are the most popular bet type among recreational bettors, and understanding their true cost is one of the biggest edges you can give yourself — because it stops you from burning money on the sportsbook's most profitable product.
The compounding vig
On a single -110 bet, the sportsbook keeps about 4.5% of the money wagered. On a parlay, the vig doesn't just add — it multiplies.
A 10-leg parlay hands the sportsbook half your expected money before a single game kicks off. No amount of handicapping skill can overcome a 50% house edge.
The payout illusion
Let's walk through a 4-leg parlay at standard -110 odds.
True odds of hitting all 4: Each leg at 50% true probability → 0.50^4 = 6.25%
Fair payout at 6.25%: (1 ÷ 0.0625) − 1 = 15-to-1
Actual sportsbook payout: approximately 12.3-to-1
The gap: You should be getting 15-to-1 but you're getting 12.3-to-1. The missing 2.7x is the compounded vig.
On every $10 parlay, the sportsbook is paying you about $123 when they should be paying $150. That's $27 per $10 bet — a 20%+ house edge. Compare that to $0.45 per $10 on a single bet.
The "almost hit" trap
Parlays are psychologically addictive because of near-misses. Going 3-for-4 on a 4-leg parlay feels like you were "so close." But mathematically, 3-for-4 pays exactly zero on a parlay. You didn't almost win — you lost entirely. Those near-misses keep you coming back, which is exactly what the sportsbook wants.
If you'd bet those same 4 legs as individual bets at 1 unit each, going 3-for-4 at -110 odds would have netted you about +1.7 units in profit. The parlay turned a winning day into a total loss.
What if each leg is +EV?
A parlay of +EV bets is technically +EV. But the variance is enormous. Even with 55% true probability on each leg (a strong edge), a 4-leg parlay only hits about 9.2% of the time. You need to accept long losing streaks before the math plays out.
For beginners, those long streaks are bankroll-threatening and psychologically brutal. Flat betting the same +EV legs individually is almost always the better approach — you collect profits incrementally instead of in rare, massive payouts.
The bottom line: The vig on parlays compounds with each leg. A 4-leg parlay carries roughly 20% vig — compared to 4.5% on a single bet. Near-misses (3 of 4 legs hitting) pay nothing on a parlay but would be profitable as individual bets. If you have 4 strong picks, bet them individually.
Run the numbers before you bet.
The BeginnerBets +EV Calculator shows you instantly whether a bet is worth placing — based on math, not gut feeling.
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