Odds calculator: odds, probability and margin
Enter odds and instantly see the probability behind them, what your stake returns and what the odds look like as fractional or American. Below, you can work out the margin of a whole market.
Convert odds
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Enter odds.
Margin of a market
How to calculate with odds
Decimal odds are standard here. They tell you directly what comes back per euro staked, stake included. €10 on odds of 2.50 returns a €25 payout if it wins, i.e. €15 net profit. The formula is simply Payout = stake × odds.
Odds are also a probability: 1 ÷ odds. Odds of 2.50 stand for 40%. Whether a bet is worth it depends on exactly that: if you rate the chance higher than the odds imply, it is a value bet from your point of view. If you rate it lower, you lose out in the long run.
Worked conversion example
| Decimal | Fractional | American | Probability |
|---|---|---|---|
| 1.50 | 1/2 | −200 | 66.7% |
| 2.00 | 1/1 (evens) | +100 | 50.0% |
| 2.50 | 3/2 | +150 | 40.0% |
| 3.40 | 12/5 | +240 | 29.4% |
| 11.00 | 10/1 | +1000 | 9.1% |
Calculate the bookmaker margin
No bookmaker offers fair odds. If you convert all outcomes of a market into probabilities and add them up, you get more than 100%. The excess is the bookmaker’s markup. An example with 2.00 / 3.40 / 3.80 for home win, draw and away win:
- 1 ÷ 2.00 = 50.0%
- 1 ÷ 3.40 = 29.4%
- 1 ÷ 3.80 = 26.3%
- Total 105.7% → payout rate 1 ÷ 1.057 = 94.6%, margin 5.4%
So of €100 staked on all three outcomes, an average of €94.60 goes back to the bettors. You get the fair odds by multiplying each price by the sum: 2.00 × 1.057 = 2.11, 3.40 × 1.057 = 3.59 and 3.80 × 1.057 = 4.02. This is the simple, proportional method. It spreads the margin evenly; in practice underdogs often carry a little more margin than the favourite.
Two-way markets such as over/under 2.5 goals, handicap or tennis match winner are calculated the same way, just with two odds. 1.90 / 1.90 gives 105.3% and therefore a 5.0% margin. Good bookmakers are at 3 to 6% in football, often well above that in niche markets.
Betting tax
Whether and how sports betting is taxed depends on the country and the bookmaker. Some bookmakers already price a tax into the odds, so you get slightly lower odds and no other deduction. Others deduct a share from the payout if you win or take it directly from the stake. Check your bookmaker’s terms before you calculate. The switch in the calculator deducts 5% from the payout: €25 then becomes €23.75, and the net profit drops from €15 to €13.75.
FAQ
How do I convert odds into a probability?
Divide 1 by the decimal odds. Odds of 2.50 correspond to 1 ÷ 2.50 = 0.40, i.e. 40%. That is the probability the bookmaker assumes including its margin. The fair probability is slightly lower.
What is the bookmaker margin?
The share the bookmaker keeps across all outcomes of a market. If you add up the reciprocals of all odds in a market, you get more than 100%. With 2.00 / 3.40 / 3.80 it is 105.7%. The payout rate is 1 ÷ 1.057 = 94.6%, so the margin is 5.4%.
How do I calculate fair odds without the margin?
Convert each price into a probability, divide it by the sum of all probabilities and take the reciprocal again. Simpler: odds × sum of the reciprocals. With a sum of 1.057, 2.00 becomes fair odds of 2.11.
What do fractional odds like 5/2 mean?
Fractional odds are common in the UK and show the net profit: 5/2 means 5 units of profit for a 2-unit stake. As decimal odds that is 5 ÷ 2 + 1 = 3.50.
How do American odds work?
Positive values show the profit on a stake of 100: +150 means 150 profit, i.e. decimal odds of 2.50. Negative values show how much you need to stake to win 100: −200 corresponds to decimal odds of 1.50.
Is betting tax deducted automatically?
That depends on the country and the bookmaker. Some already build a betting tax into the odds, others deduct a share from the winnings or from the stake. The switch “Deduct 5% tax from winnings” shows what is left after a 5% deduction.
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All information without guarantee. Betting carries a risk of loss, even at good odds.