Start with the price, not the prediction
A price answers a narrow question: how often would this bet need to win to cover its losses? At −110, risking $110 earns $100 in profit on a win. Winning 11 of 21 equal-risk bets earns $1,100 and losing 10 costs $1,100. That is a 52.38% break-even rate. It does not establish that the team has a 52.38% chance of winning.
Read American, decimal and fractional odds
Positive American odds show profit on a $100 stake; negative American odds show the stake needed to earn $100. Decimal odds include the returned stake, so decimal 2.50 means $150 profit plus $100 returned on a $100 bet. Fractional 3/2 expresses the same $150 profit. Those three formats describe the same price when American odds are +150.
Why both sides can total more than 100%
Two sides priced at −110 each imply 52.38%, a combined 104.76%. The excess is the market overround. It is not a probability distribution or a guarantee of the bookmaker’s realized profit. Use the no-vig calculator to normalize a complete two-outcome market before comparing a market estimate with your own estimate.
Check the event and settlement rules
Compare the same market, line and timestamp. A full-game moneyline is different from a first-half moneyline; a spread of −3 is different from −3.5. A draw, push, void or dead heat may change the calculation. For a win/loss bet that can push, the displayed break-even percentage applies to settled wins and losses after excluding refunded pushes.
Examples are hypothetical and rounded. These calculators explain arithmetic; they do not establish a model’s accuracy or guarantee an outcome.