Explainer
How betting odds work
Decimal, American, fractional · and what the price is really saying
An odd is a probability, written so you can be paid on it. Once you can move between the two, every format is the same information in different clothes.
Reading a price is step one
Step two is knowing whether the number is honest. Every price you read has the bookmaker's fee inside it, so the chance it advertises is always better than the chance it means. We publish the corrected figure for every football match on the board today.
Free tier covers a fifth of each day’s matches, mixed across major and minor competitions. No card needed.
Decimal odds
The simplest. The number is the total return per unit staked, your own stake included. At 2.50, a 10 stake returns 25: 15 profit and your 10 back. 2.00 is an even-money bet. Anything below 2.00 is a favourite; anything above is an underdog.
American odds
Two cases, hinged on an even-money bet.
Positive is the profit on a 100 stake. +150 pays 150 profit plus your stake, 250 in total.
Negative is the stake needed to profit 100. -200 means risking 200 to make 100, 300 back in total.
There is no price between -99 and +99; the scale jumps straight across even money.
Fractional odds
Profit over stake, the traditional British form. 3/2 pays three for every two risked, the same as 2.50 decimal. 1/1 is evens. 1/2 is “odds-on”: you risk two to make one, a heavy favourite.
The odds converter moves between all three as you type.
The probability behind the price
Divide 1 by the decimal odds. 2.50 becomes 40%. That is the chance the price is quoting, and it is the only reading that lets you compare two prices from two different formats at a glance.
The implied probability calculator does the conversion for every format.
What nobody puts on the slip
Add up the implied probabilities of every outcome of a real market. They will total more than 100% — two sides at 1.91 make 104.8%. Since exactly one outcome happens, the surplus cannot be probability. It is the bookmaker’s fee, called vigorish, and it is charged on every bet regardless of result.
Which means every price you read advertises a slightly better chance than it means. A side shown at 52.4% is really nearer 50%. The gap is not an error; it is the business model.
Reading a price honestly
Three questions answer it:
What does it pay? Multiply stake by decimal odds. What is it claiming? Divide 1 by the decimal odds. What is it charging? Add up the whole market and subtract 100.
The third is the one almost no betting site will do for you, and it is the one that changes what the first two mean.
Questions
How do betting odds work?
Odds express both a payout and a probability. In decimal format the number is the total return per unit staked, and dividing 1 by it gives the probability the price implies. A price of 2.50 returns 2.50 per unit and implies 40 percent.
How do you read betting odds?
In decimal, higher means less likely: 1.50 is a strong favourite, 5.00 is an outsider. In American, a negative price is a favourite and shows the stake needed to win 100, while a positive price is an underdog and shows the profit on a 100 stake.
What do betting odds mean?
They mean two things at once: what the bet pays if it wins, and what chance the bookmaker is quoting. The second figure always overstates the real chance, because the bookmaker's fee is built into the price.
Which odds format is best?
They carry identical information. Decimal is easiest for working out returns and comparing prices, American is standard in the United States, and fractional is traditional in Britain and Irish racing.
Do higher odds mean a better bet?
No. Higher odds mean a less likely outcome with a bigger payout. Odds describe probability and price, not quality, and no odds format tells anyone what to bet.