This odds converter changes betting odds between fractional, decimal and American formats and shows the implied probability. A second tab works out the bookmaker’s margin from the odds on a market.
- Fractional odds show profit per €1 staked, so 5/2 means €5 profit on a €2 stake.
- Decimal odds show total return per €1 staked, so 3.5 returns €3.50 including the stake.
- Implied probability is 1 divided by the decimal odds, and the total across a market is above 100% because of the bookmaker’s margin.
Type odds in any format, for example 5/2, 3.5, evens or +150, and the other formats appear instantly.
Odds formats explained
- Fractional (5/2): the profit on a winning bet compared with the stake. At 5/2 a €2 stake wins €5 profit. This is the traditional format at Irish and UK bookmakers.
- Decimal (3.50): the total return per €1 staked, including your stake. Decimal odds are the easiest to multiply for accumulators.
- American (+250): a plus number is the profit on a 100 stake, and a minus number is the stake needed to win 100.
Most bookmaker sites let you switch format in their settings. For a fuller explanation of reading prices, see our guide to how betting odds work.
Odds converter chart: common prices
| Fractional | Decimal | American | Implied probability |
|---|---|---|---|
| 1/5 | 1.20 | -500 | 83.3% |
| 1/4 | 1.25 | -400 | 80.0% |
| 1/3 | 1.33 | -300 | 75.0% |
| 1/2 | 1.50 | -200 | 66.7% |
| 4/6 | 1.67 | -150 | 60.0% |
| 4/5 | 1.80 | -125 | 55.6% |
| 5/6 | 1.83 | -120 | 54.5% |
| 10/11 | 1.91 | -110 | 52.4% |
| Evens | 2.00 | +100 | 50.0% |
| 11/10 | 2.10 | +110 | 47.6% |
| 6/5 | 2.20 | +120 | 45.5% |
| 5/4 | 2.25 | +125 | 44.4% |
| 11/8 | 2.38 | +138 | 42.1% |
| 6/4 | 2.50 | +150 | 40.0% |
| 13/8 | 2.62 | +162 | 38.1% |
| 7/4 | 2.75 | +175 | 36.4% |
| 15/8 | 2.88 | +188 | 34.8% |
| 2/1 | 3.00 | +200 | 33.3% |
| 9/4 | 3.25 | +225 | 30.8% |
| 5/2 | 3.50 | +250 | 28.6% |
| 11/4 | 3.75 | +275 | 26.7% |
| 3/1 | 4.00 | +300 | 25.0% |
| 7/2 | 4.50 | +350 | 22.2% |
| 4/1 | 5.00 | +400 | 20.0% |
| 9/2 | 5.50 | +450 | 18.2% |
| 5/1 | 6.00 | +500 | 16.7% |
| 6/1 | 7.00 | +600 | 14.3% |
| 7/1 | 8.00 | +700 | 12.5% |
| 8/1 | 9.00 | +800 | 11.1% |
| 10/1 | 11.00 | +1000 | 9.1% |
| 12/1 | 13.00 | +1200 | 7.7% |
| 16/1 | 17.00 | +1600 | 5.9% |
| 20/1 | 21.00 | +2000 | 4.8% |
| 25/1 | 26.00 | +2500 | 3.8% |
| 33/1 | 34.00 | +3300 | 2.9% |
| 50/1 | 51.00 | +5000 | 2.0% |
| 100/1 | 101.00 | +10000 | 1.0% |
How do you convert betting odds?
- Fractional to decimal: divide the top number by the bottom number and add 1. 5/2 is 5 ÷ 2 + 1 = 3.5.
- Decimal to fractional: subtract 1 and write the result as a fraction. 3.5 − 1 = 2.5, which is 5/2.
- Decimal to American: for 2.0 or more, (decimal − 1) × 100 with a plus sign. For under 2.0, −100 ÷ (decimal − 1).
- American to decimal: for a plus number, divide by 100 and add 1. For a minus number, divide 100 by the number and add 1.
What is implied probability?
Implied probability is the chance of winning that the odds suggest. Divide 1 by the decimal odds. At 5/2 (3.5) the implied probability is 1 ÷ 3.5 = 28.6%. Evens implies 50%, and 1/4 (1.25) implies 80%. Odds are the bookmaker’s price, not a forecast, so the implied probability includes their margin.
What is a bookmaker’s margin?
If you add up the implied probabilities for every outcome in a market, the total is above 100%. The amount over 100% is the bookmaker’s margin, sometimes called the overround. The lower the margin, the better the prices are for punters overall.
Take a match-result market priced at 10/11 for the home win, 13/5 for the draw and 3/1 for the away win. In decimal those are 1.909, 3.6 and 4.0. The implied probabilities are 52.4%, 27.8% and 25.0%, which add up to 105.2%. The margin is 5.2%. Use the Bookmaker margin tab above to try it with real prices. These example prices are for illustration only.
Odds-on and odds-against
Odds-against means the price is longer than evens, such as 5/2, so you win more than your stake. Odds-on means the price is shorter than evens, such as 1/2, so you win less than your stake. A €10 bet at 1/2 wins €5 profit, and a €10 bet at 5/2 wins €25 profit. Odds-on selections have an implied probability above 50%.
Shortening and drifting odds
When a price shortens, such as 5/1 going to 4/1, the selection is becoming more popular or more likely to win in the market’s view. When a price drifts, such as 4/1 going to 5/1, the opposite is true. Prices move because of bets placed, team news, weather and the going. Your bet is settled at the price you took, unless you used a best-odds-guaranteed offer on an eligible race. See how betting odds work for more.
Converting odds to work out a return
Once you have the odds in decimal, the return is simple: stake × decimal odds. A €20 bet at 11/4 is 3.75 in decimal, so it returns €75, which is €55 profit. For several selections, multiply the decimal odds together, or use our bet calculator.
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Frequently asked questions
How do you convert fractional odds to decimal?
Divide the first number by the second and add 1. For example, 5/2 is 5 ÷ 2 = 2.5, plus 1 = 3.5.
What does 5/2 mean in betting?
It means you win €5 for every €2 you stake, plus your stake back. A €10 bet at 5/2 returns €35, which is €25 profit plus your €10 stake.
What are evens odds?
Evens, also written 1/1 or 2.0 in decimal, means you win the same amount as your stake. A €10 bet returns €20 including the stake. The implied probability is 50%.
What do American odds mean?
A plus number such as +150 is the profit on a 100 stake. A minus number such as -200 is the stake needed to win 100. +150 is 5/2 and -200 is 1/2.
What is implied probability?
It is the chance of winning suggested by the odds, found by dividing 1 by the decimal odds. It includes the bookmaker’s margin, so it is not a true forecast.
What is a bookmaker’s margin?
It is the amount by which the implied probabilities in a market add up to more than 100%. It is how the bookmaker builds in a profit.
Which odds format do Irish bookmakers use?
Fractional odds are the traditional format in Ireland and the UK, and most bookmaker sites let you switch to decimal in their settings.
What are odds-on?
Odds-on means the price is shorter than evens, such as 1/2 or 4/6. You win less than your stake, and the implied probability is above 50%.
What does it mean when odds shorten?
When odds shorten, such as 5/1 going to 4/1, the price is getting smaller. It usually means the selection has become more popular with punters or is seen as more likely to win.
How do I convert decimal odds to fractional?
Subtract one from the decimal odds and write the result as a fraction. So 3.5 minus 1 is 2.5, which is 5/2. Our converter chart lists the common prices.
Last updated: 11 October 2026.
18+. Please play responsibly. Free, confidential support is available from GamblingCare.ie on 1800 936 725. Calculators are a guide only and do not guarantee what a bookmaker will pay.
