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Odds Converter: Fractional, Decimal, American Odds and a Percentage
Type a price in any box. The other three change to match, and the line underneath says what a £10 bet returns.
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Odds converter
At 5/2, a £10 win bet returns £35.00: £25.00 winnings plus the £10 stake. The price implies a 28.6% chance.
Decimal prices snap to the fraction a bookmaker would show, so 2.62 reads as 13/8 rather than 81/50.
That snapping is the part of a converter that is easiest to get wrong. Turn 2.62 into a fraction by pure arithmetic and you get 81/50, which is correct and useless: 81/50 is not a price you will see on a bookmaker’s board. The converter checks the decimal against the prices that are actually quoted and takes the one it matches, and it only falls back to plain arithmetic when a price sits well away from any of them.
Fractional odds to decimal
Fractional odds tell you the winnings for a given stake. 5/2 means you win 5 for every 2 you put on. They leave the stake out, and the decimal form puts it back in.
To convert, divide the top number by the bottom and add 1. So 5/2 is 2.5 + 1 = 3.5, and £10 at 3.5 returns £35. 7/2 is 4.5. 11/4 is 3.75. The same sum works for odds-on prices: 4/6 is 0.667 + 1, which is about 1.67.
Decimal is easier for anything with more than one bet, because you multiply straight through. A double at 5/2 and 3/1 is 3.5 × 4.0 = 14.0, so £1 returns £14. In fractions you would have to convert anyway to do it. That is why the bet calculator turns every price into a decimal before it settles anything.
Decimal odds back to fractions
Going the other way, take 1 off the decimal and write what is left as a fraction. 3.5 becomes 2.5, which is 5/2. 6.5 becomes 5.5, which is 11/2. 1.5 becomes 0.5, which is 1/2.
The trouble starts with decimals that are rounded. Exchanges and many betting sites show prices to two decimal places, so 13/8 (2.625) appears as 2.62 or 2.63, and 10/3 (4.333) as 4.33. The converter treats a decimal that is very close to a standard price as that price. It gives 9/4 for 3.25, 10/3 for 4.33 and 10/11 for 1.91. A decimal that matches nothing on the ladder, such as 2.6, is shown as the closest plain fraction, which here is 8/5.
A few steps on the ladder look strange if you are new to them. 85/40 sits between 2/1 and 9/4, at 3.125. 100/30 is the traditional way of writing 10/3, and you will still see it written that way. 15/8, 13/8 and 11/8 fill the gaps between 7/4, 6/4 and 5/4. They exist because bookmakers move prices in small steps, and a jump straight from 6/4 to 7/4 would be too coarse.
American odds
American odds, sometimes called moneyline odds, are built around a stake or a win of 100. A plus sign tells you what 100 wins: +250 wins 250, the same as 5/2. A minus sign tells you what you have to stake to win 100: −200 means risking 200 to win 100, the same as 1/2.
To convert from decimal, a price of 2.0 or more becomes (decimal − 1) × 100 with a plus sign, so 3.5 is +250. A price below 2.0 becomes −100 ÷ (decimal − 1), so 1.5 is −200. Evens is +100. You will rarely need them for British racing, but they appear on international sites and in American coverage of races like the Breeders’ Cup, where British and Irish horses often run.
A worked pair makes the minus sign clearer. A price of −150 means staking 150 to win 100. In decimals that is 1 + 100 ÷ 150, about 1.67, which is 4/6 as a fraction. A price of +400 means 100 wins 400, so the decimal is 5.0 and the fraction 4/1. Once you see that the sign only tells you which side of evens the price sits, American odds stop looking strange.
What the price says about a horse’s chance
Every price carries a claim about how likely something is. Divide 100 by the decimal odds and you get the implied chance: 3.5 is 28.6%, evens is 50%, 1/2 is 66.7%.
Add those chances up across every runner in a race and the total is always more than 100%. A six-runner race priced 2/1, 3/1, 4/1, 5/1, 6/1 and 8/1 adds up to 120.4%. The extra 20.4% is the margin built into the book, and it is the reason nobody can back every horse at those prices and come out ahead. So the implied chance is the market’s view plus the bookmaker’s cut. It isn’t a forecast, and it tells you nothing on its own about whether a horse will win.
It is still useful. If you think a horse has a one-in-three chance and the price implies one in five, you think the price is too big. Turning your own view into a price works the same sum backwards: a one-in-three chance is 3.0 in decimals, which is 2/1. If the horse is on offer at 4/1, the market is being more generous than your estimate. Whether you are right is another matter.
Converting the odds of a multiple
A double, treble or accumulator has a single combined price, and it is easiest to find in decimals. Multiply the decimal odds together: 5/2 and 3/1 make 3.5 × 4.0 = 14.0, which is 13/1 as a fraction. Three 2/1 winners make 3 × 3 × 3 = 27, or 26/1.
Convert that back into a fraction and it will often be a price that no bookmaker would quote for a single horse. A treble at 5/2, 6/4 and evens comes to 17.5, which is 33/2, or 16.5 to 1. That is fine: it is the price of the bet, not of a runner, and the ladder rule doesn’t apply. It is also why the bet calculator shows a combined figure such as “×17.5” for each line rather than a fraction.
The one thing you cannot do is add the fractions. 5/2 plus 3/1 is not the price of a double, and neither is 5/2 times 3/1 worked out as fractions (that gives 15/2). The stake has to be included at every step, which is exactly what the decimal form does.
Comparing prices from different places
Prices come in different formats depending on where you look. A newspaper racecard shows fractions, an exchange shows decimals, and an American site shows moneyline odds. To compare them, put them all in one format. Decimal is the easiest, because the bigger number is always the better price.
Is 9/4 better than 3.2? 9/4 is 3.25, so yes, by a little. Is 5/4 better than +120? 5/4 is 2.25 in decimals and +120 is 2.20, so 5/4 is better. Is 11/10 better than evens? Yes: 2.1 against 2.0. These gaps look small on one bet. Over a season of bets they are the difference between two very different totals.
One thing to watch: exchange prices are shown before commission is taken from winnings, so a decimal price on an exchange is worth slightly less than the same number at a fixed-odds bookmaker.
Common prices at a glance
| Fractional | Decimal | American | Implied chance |
|---|---|---|---|
| 1/5 | 1.20 | −500 | 83.3% |
| 2/5 | 1.40 | −250 | 71.4% |
| 1/2 | 1.50 | −200 | 66.7% |
| 4/6 | 1.67 | −150 | 60.0% |
| 4/5 | 1.80 | −125 | 55.6% |
| 10/11 | 1.91 | −110 | 52.4% |
| Evens | 2.00 | +100 | 50.0% |
| 6/5 | 2.20 | +120 | 45.5% |
| 6/4 | 2.50 | +150 | 40.0% |
| 13/8 | 2.63 | +163 | 38.1% |
| 2/1 | 3.00 | +200 | 33.3% |
| 5/2 | 3.50 | +250 | 28.6% |
| 3/1 | 4.00 | +300 | 25.0% |
| 7/2 | 4.50 | +350 | 22.2% |
| 4/1 | 5.00 | +400 | 20.0% |
| 5/1 | 6.00 | +500 | 16.7% |
| 8/1 | 9.00 | +800 | 11.1% |
| 10/1 | 11.00 | +1000 | 9.1% |
| 20/1 | 21.00 | +2000 | 4.8% |
13/8 is exactly 2.625 in decimals and +162.5 in American odds. The table rounds both.
Reading prices on a racecard
Newspaper and online racecards print a betting forecast, and the result lists the starting prices. Both use a few short labels you won’t find in the converter.
“Fav” marks the favourite, the horse with the shortest price. When two horses share it, they are joint favourites, printed “jt-fav”, and three or more are co-favourites. “Evens fav” means the favourite went off at evens. A price with “op” in front of it, such as “op 4/1”, is the opening price: the horse started at 4/1 and ended up somewhere else.
The favourite’s price is worth converting. A favourite at 6/4 is a 40% chance on the market’s view, which still leaves it more likely to lose than to win. Even an odds-on favourite at 4/6 carries a 40% implied chance of being beaten. Favourites win a lot of races, but a short price is a statement about the field, not a promise.
The betting forecast itself is a newspaper’s estimate of how the market will open, made before any bets are struck. It is useful as a guide to which horses are fancied, and it is not a price anyone will pay you. The prices you can actually take are the ones a bookmaker offers on the day, and the result shows the starting prices.
Odds-on, evens and odds-against
A price shorter than evens is odds-on: you win less than you stake, and the decimal is below 2.0. A price longer than evens is odds-against. Evens itself sits in the middle, a straight double-your-money bet.
The words for price changes come from the same idea. A horse that is shortening is moving towards odds-on as money comes for it. One that is drifting is getting longer as the market loses interest. A horse backed from 6/1 to 7/2 has shortened from 14.3% to 22.2% implied, which is a big move. Racing coverage talks about those moves a lot. The converter is a quick way to see how big they really are.
If you take a price, that is what you are paid at, whatever happens to the market afterwards. If you don’t, you get the starting price, and starting price explained covers how that works. For the wider picture of how UK racing odds are read, start at horse racing odds explained.