How parlay odds are calculated
A parlay multiplies each leg's decimal odds together — every leg must win. Two -110 legs combine to +264, which implies about 27.5%. Books love parlays because the hold compounds with every leg you add.
When a parlay is worth the price
That doesn't make every parlay wrong. It makes the price the thing to check: if the legs are correlated or each leg is independently +EV, the multiplication can work for you instead of against you. Big Mike's engine prices each leg against no-vig fair value before it ever suggests one.
