Every football price tells you two things: how much you would get back if your bet won, and how likely the bookmaker thinks that outcome is. Once you can read both, a list of odds stops being a wall of numbers and becomes a view of the match that you can question. This guide covers fractional odds, decimal odds, how to turn either into a percentage, and how to spot the margin a bookmaker builds into its prices. The examples use real prices for a Bundesliga game, Mainz against Bayern Munich, taken from the bookmaker grid on our Mainz v Bayern Munich fixture page.
Fractional odds
Fractional odds are the traditional British format, and you will still see them in betting shops and on television. They tell you the profit for each unit you stake. At 5/1, often said as five to one, a £1 bet wins £5 profit, and you also get your £1 stake back, so £6 in total. At 11/2, a £2 bet wins £11. When the first number is smaller than the second, as with 2/5 or 3/10, the price is odds-on: the bookmaker thinks the outcome is more likely to happen than not, and you have to stake more than you stand to win. At 2/5, a £5 bet wins £2 profit. A price of 1/1 is called evens, which means you win the same amount as you stake. Fractions are easy to say out loud but awkward to compare, because it is not obvious at a glance whether 11/8 is longer than 7/5.
Decimal odds
Decimal odds, used by betting exchanges and most comparison sites, including ours, give the total return for each unit staked, with the stake already included. A £10 bet at 6.50 returns £65 if it wins, which is £55 profit plus your £10 back. A £10 bet at 1.30 returns £13. That makes decimal prices easier to compare: a bigger number always pays more. To convert, add one to the fraction. So 5/1 is 6.00, 11/2 is 6.50, evens is 2.00, 2/5 is 1.40 and 3/10 is 1.30. To go the other way, take one away and turn the remainder into a fraction: 2.25 becomes 1.25, which is 5/4. If you see American odds such as +150 or minus 200 on a US site, +150 means £150 profit on a £100 stake, which is 2.50 in decimal, and minus 200 means you stake £200 to win £100, which is 1.50.
From a price to a percentage
Every price can be turned into the chance the bookmaker is implying. With decimal odds, divide 100 by the price. William Hill's prices for Mainz v Bayern, as listed on our grid when it was last updated at 13:16 GMT on Friday 6 November, were 6.50 for Mainz, 6.00 for the draw and 1.30 for Bayern. That works out at about 15.4 per cent for a Mainz win, 16.7 per cent for a draw and 76.9 per cent for Bayern. With fractional odds, divide the second number by the sum of both: 5/4 is four divided by nine, about 44 per cent. This is the most useful habit in reading odds, because it turns a price into a claim you can test. If you think Mainz win this game more often than about three times in 20, the price looks long to you. If you think they win it less often, it looks short. The percentage is the bookmaker's view, not a fact about the match.
The bookmaker's margin
Add up those three William Hill percentages and you get about 109 per cent, not 100. The extra nine per cent or so is the bookmaker's margin, sometimes called the overround. It is how a bookmaker makes money over time whichever result comes in: each price is a little shorter than the true chance alone would justify. Bet Victor's prices for the same game, 5.50, 5.00 and 1.40, add up to about 110 per cent. Margins vary between bookmakers, between markets and between games, and they tend to be higher on less popular markets than on the match result. You can work out the margin for any market in a few seconds, and it is worth doing. A market that adds up to 105 per cent is giving you better value overall than one that adds up to 112, even if one individual price looks generous. The margin is also why a bookmaker's implied percentages always overstate the chance of each outcome slightly.
Why comparing prices matters
Our fixture pages list the best price for each result and then every bookmaker side by side, because prices for the same outcome can differ a lot. For Mainz v Bayern, the 21 bookmakers on our grid offered a Mainz win at anything from 5.50 to 8.20. A £10 bet at 8.20 returns £82, against £55 at 5.50, for exactly the same outcome. Take the best price for each result, 8.20 for Mainz, 7.20 for the draw and 1.40 for Bayern, and the three percentages add up to about 97.5, below 100, because no single bookmaker was offering all three. Betting exchanges such as Smarkets and Matchbook often show prices close to 100 per cent: Smarkets' three prices for this game added up to about 100.7. Exchanges charge commission on winnings, though, so the headline price is not quite what you receive. Prices also move as team news and money arrive, so a price is only true at the moment it was captured.
Putting it together
When you look at a fixture, start with the match result prices and turn them into percentages. Check how much they add up to, so you know the size of the margin. Then compare the best available price for the outcome you are interested in with what you know about the match: form, injuries, head to head and the referee. All of that is on our fixture pages, for example in our Mainz v Bayern Munich preview, which works through the same prices used here. The same steps apply to other markets, such as both teams to score or over 2.5 goals. Our guide to shots and shots on target covers one way to read the match statistics behind those markets. Reading odds well does not make betting safe. It only helps you see what a price is really saying, and decide whether you agree with it.
Bet responsibly
Odds are a bookmaker's view of the chances, not a promise, and no market removes the risk of losing. Only bet what you can afford to lose, set limits before you start, and never chase losses. Betting is for over-18s. If gambling stops being fun, contact the National Gambling Helpline on 0808 8020 133 or visit BeGambleAware.org. More about how TotalOdds works is on our about page.
Photo credits
The cover shows the view from behind the goal at the Emirates Stadium in September 2011. Photograph by Ronnie Macdonald, CC BY 2.0, via Wikimedia Commons, adapted with text.
