Multis: why the bookies love them

A multi multiplies the decimal odds of each leg, which feels like leverage. What it also multiplies is the margin. If each leg carries a 5% house edge, a four-leg multi carries roughly a 19% combined edge against you — nearly four times the disadvantage of a single.

The maths of compounding probability is brutal. Four legs that are each genuinely 70% likely combine to just a 24% chance of all landing. Punters consistently overestimate multi chances because each leg individually looks safe.

That's why bookmakers promote multis so heavily — boosted odds, "multi builder" tools, social sharing. The product with the loudest marketing is reliably the one with the widest margin.

If you bet for entertainment, a small multi is fine entertainment — just price it as such. If you bet for profit, singles on markets where you've found genuine value will always beat stacking correlated hope.