How betting odds work
Decimal, fractional and American odds explained with worked examples, plus how to turn any price into the probability it implies.
By the Sportsbooks Editorial Team · Updated October 27, 2026
Odds tell you two things at once: how much a winning bet pays, and how likely the sportsbook thinks the outcome is. The three formats you will meet, decimal, fractional and American, are different ways of writing the same price.
Decimal odds
Decimal odds show the total return for each unit staked, including your stake. They are standard in Europe, Canada and Australia, and most sportsbooks let you switch to them.
- A 10 stake at 2.50 returns 25: 15 profit plus the 10 stake.
- A 10 stake at 1.40 returns 14: 4 profit plus the 10 stake.
The maths is one line: return = stake × decimal odds.
Fractional odds
Fractional odds, traditional in UK and Irish betting shops, show the profit relative to the stake. The stake comes back on top.
- 3/2 ("three to two") pays 3 profit for every 2 staked. A 10 stake returns 15 profit plus the 10 stake: 25 in total.
- 1/2 ("two to one on") pays 1 for every 2 staked. A 10 stake returns 15 in total.
- Evens is 1/1: profit equals the stake.
To turn fractional into decimal, divide and add 1: 3/2 = 1.5, plus 1 = 2.50.
American odds
American (moneyline) odds use 100 as the reference stake and carry a sign.
- Positive (+150): the profit on a 100 stake. +150 wins 150, so the bet returns 250.
- Negative (−200): the stake needed to win 100. −200 means staking 200 to win 100, returning 300.
To convert to decimal: for positive odds, divide by 100 and add 1 (+150 → 2.50). For negative odds, divide 100 by the number and add 1 (−200 → 1.50).
The same prices in all three formats
| Decimal | Fractional | American | Implied probability |
|---|---|---|---|
| 1.50 | 1/2 | −200 | 66.7% |
| 1.91 | 10/11 | −110 | 52.4% |
| 2.00 | 1/1 (evens) | +100 | 50.0% |
| 2.50 | 3/2 | +150 | 40.0% |
| 3.00 | 2/1 | +200 | 33.3% |
| 5.00 | 4/1 | +400 | 20.0% |
From odds to probability
Every price implies a probability: 1 ÷ decimal odds. A price of 2.50 implies 1 ÷ 2.50 = 40%.
This is the most useful thing odds tell you. If you think a team wins more often than the implied probability, the price may be good value; if less often, it isn't, however big the payout looks.
The implied probabilities of every outcome in one market add up to more than 100%. The extra is the sportsbook's margin, explained in our guide to the bookmaker margin.
Try any price in the odds converter: it accepts all three formats.
Frequently asked questions
What does +200 mean in betting?
A 100 stake wins 200 in profit, so it returns 300 in total. As decimal odds that is 3.00, and as fractional odds 2/1. The implied probability is 33.3%.
What does -150 mean in betting?
You must stake 150 to win 100 in profit, so a winning bet returns 250. As decimal odds that is 1.67, and the implied probability is 60%.
Which odds format is best?
They all describe the same price, so none gives better value. Decimal odds are the easiest to compare and to multiply in accumulators, which is why many bettors switch to them in their account settings.