The Math Behind the Payout
Parlay odds multiply: three -110 legs pay about +596. But fair odds for three 52.4% events would be +616 — the book's edge compounds with every leg. Standard vig of ~4.5% per leg becomes roughly 13% on a three-leg parlay and over 30% on six legs.
Same-Game Parlays: Extra Caution
SGPs correlate legs (a QB's passing yards and his team winning), and books price that correlation in-house — usually conservatively in their favor. Boosted SGP promos can offset this, but unboosted SGPs typically carry the worst hold percentages on the entire site.
When a Parlay Is Defensible
Genuinely correlated legs the book underprices, promo boosts that push payouts past fair odds, and small entertainment stakes are the legitimate cases. As a bankroll strategy, flat single bets outperform parlays over any meaningful sample.