How Betting Odds Work

Every price you will ever see at a bookmaker is a probability wearing a disguise. Once you can take the disguise off, three different formats stop being confusing and start being the same number written three ways.

Decimal odds

Decimal is the format we use across this site because it needs no arithmetic to read. The number is your total return for every £1 staked, stake included. A price of 2.50 returns £2.50 on a £1 bet — £1.50 of winnings plus the £1 you put down. A price of 1.50 returns £1.50, so the winnings are 50p.

To convert any decimal price into a probability, divide one by it. 2.50 becomes 40%. 1.50 becomes 66.7%. That percentage is what the bookmaker is telling you it thinks the chance is, plus its margin — a subject that gets its own guide.

Fractional and American

Fractional odds are the British tradition: 6/4 means you win £6 for every £4 staked, and the stake comes back on top. Add the two numbers and divide by the second to get the decimal — 6/4 is 10 ÷ 4 = 2.50. American odds put a plus or minus in front of a three-figure number: +150 means £150 won on a £100 stake, −200 means £200 staked to win £100. Both are 2.50 and 1.50 in decimal.

Why the probability is what matters

Two bookmakers can show you 6/4 and 2.45 for the same outcome and most people will not notice they are different prices. Converted to probabilities they are 40% and 40.8%, and the second one is worse for you. Every guide on this site assumes you have done this conversion, because it is the only way to compare what you are actually being offered.

• Switch every bookmaker account you hold to decimal in the settings. It removes a step from every comparison.
• A shorter price is a bigger probability — and a bigger share of your stake kept by the bookmaker if it is wrong.
• The prices in a market always add up to more than 100%. That excess is the margin, and it is the subject of the next guide.