Free Odds Converter Calculator
Convert fractional, decimal, American, implied probability and Hong Kong odds instantly. Free — no sign-up needed.
e.g. 5/2, 11/4, 7/1
e.g. 3.50, 1.91, 6.00 — always greater than 1.00
Positive (+250) = underdog. Negative (−110) = favourite.
Enter a percentage between 0.1 and 99.9
e.g. 2.50 — same as decimal odds minus 1
Odds Converter
Choose the odds format you already have — fractional, decimal, American, implied probability or Hong Kong.
Type in the odds value. For fractional odds, enter the numerator and denominator separately. The converter updates live as you type.
See all five formats, the implied probability bar and a £10 return calculation update in real time.
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Betting Tools
What Are Betting Odds?
Betting odds are a numerical expression of the probability of a given outcome occurring, set by a bookmaker. They serve two purposes simultaneously: they communicate the bookmaker’s estimate of how likely something is to happen, and they define exactly how much you stand to win relative to your stake. Every time you see a price on a football match, a horse race or a tennis tournament, you are looking at an odds expression — the question is simply which format it is presented in.
In the United Kingdom, you will encounter odds in multiple formats depending on where you are betting. Traditional high street bookmakers built their reputation on fractional odds, while betting exchanges like Betfair use decimal odds as standard. If you follow American sports or use international sportsbooks, you will regularly encounter moneyline (American) odds. Our odds converter handles all of these instantly so you never have to perform the mental arithmetic yourself.
Fractional Odds Explained
Fractional odds are the traditional British format and remain dominant in horse racing. Written as two numbers separated by a slash — for example 5/2, 11/4, or 7/1 — the first number (numerator) represents your profit if the second number (denominator) is staked. At 5/2, a £2 stake returns £5 profit plus your £2 stake back — a total return of £7. To convert to decimal, divide the numerator by the denominator and add 1: 5 ÷ 2 + 1 = 3.50.
When the numerator is smaller than the denominator (e.g. 1/2, 2/5), the selection is odds-on — meaning the bookmaker considers it more likely to win than not. Odds-on bets return less than double your stake. Check our horse racing guides for more on reading racing markets where fractional odds dominate.
Decimal Odds Explained
Decimal odds are the standard across continental Europe, betting exchanges, and increasingly as the default on UK sportsbooks. Multiply your stake by the decimal odds to get your total return including stake. A decimal of 3.50 on a £10 bet returns £35.00 total. Decimal odds are strongly preferred for matched betting and arbitrage because the maths is simpler — our free bet calculator uses decimal odds as its primary input for this reason.
American (Moneyline) Odds Explained
American odds use positive and negative whole numbers relative to a £100 stake. Positive odds (+250) show profit on a £100 bet — so +250 returns £250 profit. Negative odds (−150) show how much you must stake to win £100 profit. UK bettors encounter these most often on NBA, NFL, MLB and NHL markets. Use the American tab above to convert any moneyline price instantly.
Implied Probability and Finding Value
Implied probability converts odds into the bookmaker’s estimated percentage chance of an outcome occurring. The formula is: 1 ÷ Decimal Odds × 100. So 3.50 decimal = 28.57% implied probability. If you believe something has a higher chance than the bookmaker implies, that represents a value bet. The sum of implied probabilities across all outcomes in a market always exceeds 100% — that excess is the bookmaker’s overround or margin, typically 3–10% on major markets. Use our bankroll management calculator to size stakes appropriately when value betting.
Hong Kong Odds Explained
Hong Kong odds are simply decimal odds minus 1 — they represent profit per unit staked in decimal form. HK odds of 2.50 equal decimal 3.50, fractional 5/2. They are standard across Asian betting markets and occasionally appear on international exchanges. UK bettors most commonly encounter them on Betfair’s Asian markets or when using international platforms.
Odds Format Comparison Table
| Fractional | Decimal | American | Implied % | £10 Return |
|---|---|---|---|---|
| 1/2 | 1.50 | −200 | 66.67% | £15.00 |
| Evens | 2.00 | +100 | 50.00% | £20.00 |
| 6/4 | 2.50 | +150 | 40.00% | £25.00 |
| 5/2 | 3.50 | +250 | 28.57% | £35.00 |
| 4/1 | 5.00 | +400 | 20.00% | £50.00 |
| 10/1 | 11.00 | +1000 | 9.09% | £110.00 |
| 33/1 | 34.00 | +3300 | 2.94% | £340.00 |
Using the Odds Converter for Betting Exchanges
Betting exchanges (Betfair, Smarkets, Betdaq) always use decimal odds. When backing from a bookmaker and laying on an exchange for matched betting, you need to compare prices in the same format. Our converter lets you check any bookmaker’s fractional price against the exchange decimal in one step. See our free bet calculator for the full matched betting calculation including lay stake and liability.
Odds Formats by Sport
Horse racing in the UK predominantly uses fractional odds — on-course bookmakers, ITV Racing coverage and most racing platforms display prices as 11/4, 9/2 and so on. Football betting has shifted almost entirely to decimal online. NBA, NFL and other American sports markets often appear in moneyline format even on UK platforms because data feeds provide them that way first. For each-way horse racing bets, use our each-way calculator alongside this converter to account for place terms.
Responsible Gambling and Understanding Odds
Understanding that odds of 10/1 imply only a 9.09% chance of winning means accepting that you would expect to lose roughly nine times in every ten bets at that price. Knowing this helps you make informed decisions about stake sizes and betting bank management. All bookmakers featured on Got The Odds are licensed by the UK Gambling Commission. Visit our responsible gambling page for further resources, or contact BeGambleAware.org if you need support.
Questions
Fractional odds (e.g. 5/2) show profit relative to your stake. Decimal odds (e.g. 3.50) show your total return per £1 staked including stake back. To convert, divide the numerator by the denominator and add 1. Use our free bet calculator for matched betting calculations in decimal format.
For positive American odds (e.g. +250): divide by 100 to get fractional profit per £1 staked — +250 = 5/2. For negative odds (e.g. −110): divide 100 by the absolute value — −110 = 10/11. Our converter handles this instantly — just select the American tab and enter your odds.
Implied probability is the bookmaker’s estimated likelihood of an outcome as a percentage. Odds of 5/2 (decimal 3.50) imply a 28.57% chance of winning. Adding up the implied probabilities of all outcomes in a market gives a figure above 100% — the excess is the bookmaker’s margin. Spotting value means finding selections where you believe the true probability is higher than the implied figure.
Hong Kong odds are simply decimal odds minus 1 — they represent profit per unit staked in decimal form. Decimal 3.50 equals Hong Kong 2.50. Common in Asian betting markets, UK bettors most often encounter them on Betfair’s Asian markets or international sportsbooks.
Fractional odds remain dominant in horse racing but most UK online bookmakers now default to decimal, with the option to switch in account settings. Check our bookmaker reviews for a full comparison of leading UK betting sites including odds formats and available markets.
Enter the bookmaker’s price (often fractional) into the converter to get the decimal equivalent, then use that decimal figure in our free bet calculator alongside the exchange lay odds. Decimal format is essential for accurate matched betting calculations as it makes lay stake and liability formulas straightforward.