How betting odds work: what they are and how to use them
We’ve followed social sportsbooks and sweepstakes casinos since they first started launching, and remain ahead of the game with rating the best prediction market apps. From Missouri sports betting to emerging markets, we provide actionable intel on where and how you can bet securely and legally. Making a profit in gambling involves predicting the relationship of the true probabilities to the payout odds. The numerator and denominator of fractional odds are often integers, thus if the bookmaker’s payout was to be £1.25 profit for every £1 stake, this would be equivalent to £5 profit for every £4 staked, and the odds would therefore be expressed as 5/4. Before you rely on one, check how many bookmakers it covers, how quickly the prices are refreshed, whether it shows markets beyond the match result and whether it keeps the history of every price move.
Odds can also be expressed as a number, by dividing the terms in the ratio—in this case it is unique (different fractions can represent the same rational number). For example, “odds of a weekend are 2 to 5”, while “chances of a weekend are 2 in 7”. Implied by this definition is the fact that the probability of an event is given by the ratio of favourable outcomes to the total number of possible outcomes. If k is any positive number then X to Y is the same as kX to kY, and similarly if “to” is replaced with “in” or “for”. Multiplying these probabilities by 100% gives the percentage.
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However, in more variable situations, such as a multi-runner horse race or a football match between two unequally matched teams, betting “at odds” provides the possibility to take the respective likelihoods of the possible outcomes into account. Similarly, fair betting odds can be expressed as “(1−p)/p to 1”, “1/p for 1”, “+100(1−p)/p”, “−100p/(1−p)”, “D−N to N”, “D for N”, “+100(D−N)/N”, or “−100N/(D−N)”. In gambling, odds are often given as the ratio of the possible net profit to the possible net loss, and sometimes this is called fractional odds.
Sports information services are often used by professional and semi-professional sports bettors to help achieve this goal. It was about 3.7% less for wins by the visitors, and 5.7% less for draws. A study on soccer betting found that the probability for the home team to win was generally about 3.4% less than the value calculated from the odds (for example, 46.6% for even odds). The total of these three percentages is 100%, thus representing a fair ‘book’. In a 3-horse race, for example, the true probabilities of each of the horses winning based on their relative abilities may be 50%, 40% and 10%. In formulating the odds to display the bookmaker will have included a profit margin which effectively means that the payout to a successful bettor is less than that represented by the true chance of the event occurring.
Our tennis odds page compares the prices on every match of the day, next to past results and the odds they closed at. In tennis we follow the ATP and WTA tours every week, the Challenger and ITF events in between and the four Grand Slams, from the Australian Open to Wimbledon and the US Open. For beginners, our bet calculator shows the payout of a bet, for a single or an accumulator, in decimal, fractional or American odds. Enter how much you want to wager in total to see the stake for each outcome and the resulting profit. Our sure bets page shows a way to cover every outcome of a match across different bookmakers so that the combined odds return a profit, as long as the prices are still available when you place the bets. Our real-time data updates live scores as soon as a goal is scored, a point is won or a basket is made, and with live odds available for matches in-play, you can compare prices during a match and before it.
Some bets involve combining multiple outcomes for higher rewards, while others target specific in-game events or achievements. Once you’re familiar with the basic math, fractional odds become an easy way to see potential profits relative to the stake. They’re especially popular in horse racing, where bettors often look for value in underdog picks or assess returns more precisely using this format. Fractional odds can be a bit trickier to calculate quickly, but they’re favored by many bettors for how clearly they represent the risk-reward ratio. If you bet $10 at 7/2, you’d get $35 in profit plus your initial $10 back, totaling $45.
When probability is expressed as a number between 0 and 1, the relationships between probability p and odds are as follows. When Moneyline odds are quoted as a positive number +X, non gamstop sports betting it means that a wager pays X to 100. However in many situations, the possible loss (“stake” or “wager”) is paid up front and, if the gambler wins, the net win plus the stake is returned.