Definition
True Odds
Also known as Fair Odds, Real Odds
By Abhinav VasudevanReviewed Editorial policy
In short
True odds are the actual mathematical probability of an outcome, as opposed to the odds a bookmaker offers. The gap between the two is the house edge, and in casino games it is exactly calculable.
True odds are what a fair bet would pay. Offered odds are what you actually get. Everything the gambling industry earns lives in the difference.
In casino games the gap is exact
Roulette makes this visible. A single number on a European wheel has 37 pockets, so the true odds are 36 to 1. The casino pays 35 to 1.
That single unit of shortfall, spread across 37 spins, is the 2.70% house edge. Nothing is hidden or uncertain about it. The numbers are published, the wheel is what it is, and the shortfall is structural.
Craps does the same more sharply. Rolling a 12 is a 1-in-36 event, so true odds are 35 to 1. Most tables pay 30 to 1, giving that bet a house edge of about 13.9%.
The one exception worth knowing is the craps odds bet, taken behind a pass line wager. It pays exactly true odds, with zero house edge. It is the only bet on a casino floor that does, and it exists only because you cannot place it without first making a bet that does carry an edge.
In sports betting nobody knows them
The critical difference: in casino games true odds are calculable, and in sports they are not.
Nobody knows the real probability that a football team wins. The best available estimate is the market itself the aggregate of every bet placed, weighted by money. Devigging the market price strips out the overround and recovers that estimate.
A bet is only worth placing if your own assessment beats the devigged market number, not merely the quoted price. That is a much harder bar, and it is the real reason sports betting is difficult.
Common questions
What are the true odds in roulette?
A single number on a European wheel has 37 pockets, so true odds are 36 to 1. The casino pays 35 to 1. That one missing unit, spread across 37 spins, is the entire 2.70% house edge.
Can you calculate true odds in sports betting?
No, and that is the central difficulty. Nobody knows the real probability that a team wins. The best available estimate is the market itself, which is why devigging a sharp book is the practical substitute.