Odds Converter: Fractional, Decimal and American Odds Calculator

A bare whole number is read as odds-against with a stake of 1, so 5 means 5/1. A plus or minus sign means American, a slash or the word evens means fractional, and a decimal point means decimal. For 11/4 you get 3.75 in decimal, +275 in American and an implied chance of 26.67%.

When you enter a decimal or American price, the converter also shows it "As a fraction". Most of the time that is an exact match: 3.75 is 11/4 and +175 is 7/4. Some decimals have no clean fraction, and then the converter gives the exact figure plus the nearest traditional UK price. Typing 1.91 returns 91/100 and points to 10/11, which is the price a bookmaker would actually quote. Typing 2.5 returns 3/2 and the quoted form 6/4.

Think of it as an odds calculator for notation, not a betting odds calculator for stakes. The converter does not know which bookmaker or market a price came from, and it does not add or remove margin. It translates one price from one notation into another, nothing more. If you only have a few seconds, the table of common prices further down covers most of what people look up.

Scale the fraction to any stake you like. At 11/4 a £10 stake gives £27.50 profit and £37.50 back. For 5/2, every £2 staked wins £5, so £10 wins £25 and returns £35.

A fractional price below 1 means the profit is smaller than the stake, as with 1/2: stake £2 to win £1, £3 back. Those are the odds-on prices. A price above 1, such as 5/2 or 50/1, means the profit is bigger than the stake, which is odds-against. Evens (1/1) sits in the middle: the profit equals the stake.

Converting fractional to decimal odds for a whole slip is the same sum repeated for each leg. Going the other way, subtract 1 from the decimal price and turn the remainder into a fraction. For 3.75 that leaves 2.75, which is 11/4. For 2.50 it leaves 1.5, which is 3/2 (and is quoted as 6/4 in UK shops). For 1.91 it leaves 0.91, which has no neat form, and that is why the converter falls back to 91/100 and the nearest quoted price, 10/11.

Decimal odds are the standard on exchanges and in most of continental Europe, and many UK bookmakers let you switch the whole site to decimal in the account settings. They make comparison quicker: 3.75 against 3.50 is obviously better, while 11/4 against 5/2 needs a second's thought.

You meet them on US sports coverage, on American betting news and in the moneyline, spread and totals markets that US sportsbooks publish. A UK reader sees them when following a US league or when a site quotes prices in the home market's notation. The smallest American price is +100, which is evens; there is no such thing as +50 or −50.

Positive prices are odds-against and negative ones are odds-on, the same split that fractional odds have around evens. The two shapes of the same number are linked by 100: +200 is 2/1, and −200 is 1/2.

1/2 in decimal odds is 1.50, because 1 ÷ 2 = 0.5 and 0.5 + 1 = 1.5. 6/4 odds in decimal are 2.50 (6 ÷ 4 = 1.5), and 11/8 odds in decimal are 2.375, which a bookmaker shows as 2.38. 13/8 odds in decimal are 2.625, also shown as 2.63.

Because the fractions 6/4 and 3/2 are the same number, they share a decimal price of 2.50. Bookmakers still print 6/4, for reasons covered a little further down. If you need a betting odds calculator that takes a stake, the bet calculator does that part.

The same price carries an implied chance of 1.96%, or roughly 1 in 51. That is how the bookmaker prices the outcome, not a prediction of how often it will happen, since the figure includes the bookmaker's built-in margin. Long odds like 50/1 are common on outright markets and on accumulators with a few legs; they pay a lot because the outcome is unlikely.

A bet at 50/1 loses far more often than it wins. If you are placing one, stake an amount you can afford to lose and set your limit first. Gambling advice and support are covered on our responsible gambling page.

From a fraction, put the second number over the sum of both: 4 ÷ (11 + 4) = 26.67% for 11/4. From American odds, +175 gives 100 ÷ 275 = 36.36%, and −200 gives 200 ÷ 300 = 66.67%. The short cut is to work in decimal and divide into 1.

Treat the result as the bookmaker's price converted into a percentage, not as the true chance. The true probability of a team winning is unknown, and every price has a margin folded into it. That is where the figures in the next section come from.

The same holds in bigger markets. A three-way football price of 2.10, 3.40 and 3.60 gives 47.62% + 29.41% + 27.78% = 104.81%. Those percentages are not probabilities, which would have to total 100%, and they show the bookmaker's built-in edge. The odds converter reports each price on its own and does not remove the margin.

Comparing the overround across shops is one way to see which prices are tighter. The betting odds explained guide goes through margin, value and how to read a price board in more depth.

Odds-against are prices bigger than evens, such as 5/2, 11/4 or 50/1. The profit exceeds the stake, and the implied chance sits below 50%. Odds-on are prices shorter than evens, such as 1/2, 4/6 or 10/11. The profit is smaller than the stake and the implied chance is above 50%. Staking £6 at 4/6 wins £4 and returns £10.

In decimal the split is easy to spot: anything under 2.00 is odds-on, anything over 2.00 is odds-against. In American odds the sign tells you, minus for odds-on and plus for odds-against.

The converter keeps what you typed: enter 6/4 and it shows 6/4, enter 4/6 and it shows 4/6. Maths is done on the reduced form, which is why 6/4 and 3/2 give the same 2.50 decimal and 40.00% chance. A price that arrives as decimal or American is shown as its exact fraction, with the nearest quoted price beside it when the two differ.

The nearest quoted price is a guide for reading, not a conversion. 1.91 is 91/100 exactly and 10/11 on the ladder, and the two differ by less than 0.001 in decimal terms.