Quick answer: to work out a bet, multiply your stake by the decimal odds to get your total return; take away the stake to get your profit. A €10 bet at 2.50 (6/4 or +150) returns €25, a €15 profit. The odds also tell you the chance the bookmaker gives: 1 ÷ 2.50 = 40%. Use the odds calculator below to convert decimal, fractional and American odds and see your returns on any stake.
Returns include your stake. Works for a single bet; for an accumulator, multiply the decimal odds of each leg and enter the total.
Fair odds remove the margin in proportion to each price. Lower margins mean better value for bettors.
How to use the odds calculator
- Choose the odds format your bookmaker shows: decimal (2.50), fractional (6/4), American (+150) or an implied chance in percent.
- Type the odds and your stake. The screen shows your total return, your profit and the same odds in the other two formats.
- Switch formats at any time: the odds you entered are converted automatically.
- Check the margin of a whole market in the second calculator by entering the decimal odds of every outcome.
Odds formats explained
All three formats describe the same price; they just show it differently. Decimal odds are the easiest for working out returns, fractional odds are traditional in UK and Irish racing, and American (moneyline) odds are standard in the US.
- Decimal: the total you get back for every 1 staked, including the stake. 2.50 returns 2.50 for each 1 you bet.
- Fractional: the profit compared with the stake. 6/4 means you win 6 for every 4 staked, plus your stake back.
- American: a plus number shows the profit on a 100 stake (+150 wins 150); a minus number shows how much you must stake to win 100 (−200 means stake 200 to win 100).
Odds conversion chart
| Fractional | Decimal | American | Implied chance |
|---|---|---|---|
| 1/2 | 1.50 | −200 | 66.7% |
| 4/6 | 1.67 | −150 | 60.0% |
| 10/11 | 1.91 | −110 | 52.4% |
| 1/1 (evens) | 2.00 | +100 | 50.0% |
| 6/4 | 2.50 | +150 | 40.0% |
| 2/1 | 3.00 | +200 | 33.3% |
| 5/2 | 3.50 | +250 | 28.6% |
| 3/1 | 4.00 | +300 | 25.0% |
| 5/1 | 6.00 | +500 | 16.7% |
| 10/1 | 11.00 | +1000 | 9.1% |
How to convert odds by hand
| From | To | Formula | Example |
|---|---|---|---|
| Fractional a/b | Decimal | a ÷ b + 1 | 5/2 → 2.5 + 1 = 3.50 |
| Decimal d (2.00 or more) | American | +(d − 1) × 100 | 3.50 → +250 |
| Decimal d (below 2.00) | American | −100 ÷ (d − 1) | 1.50 → −200 |
| American +A | Decimal | A ÷ 100 + 1 | +150 → 2.50 |
| American −A | Decimal | 100 ÷ A + 1 | −110 → 1.91 |
| Decimal d | Implied chance | 100 ÷ d | 2.50 → 40% |
Working out bet returns
With decimal odds, return = stake × odds and profit = return − stake. With fractional odds a/b, profit = stake × a ÷ b. So €20 at 9/4 makes a profit of €20 × 9 ÷ 4 = €45, and you get €65 back in total.
For an accumulator (called a parlay in the US), multiply the decimal odds of every selection. Three legs at 2.00, 1.50 and 1.80 give combined odds of 2.00 × 1.50 × 1.80 = 5.40, so a €10 acca returns €54 if all three win. Enter 5.40 in the calculator to check. Remember that every leg must win, and the bookmaker's margin is multiplied too.
Implied probability and value bets
Implied probability is the chance of winning that the odds suggest. Odds of 2.50 imply 40%: if you think the real chance is higher, the bet has value; if it's lower, you're paying too much. Over hundreds of bets, only value bets make money, which is why comparing prices between bookmakers matters more than any single tip. Our sports betting tips explain this in more detail.
Bookmaker margin (overround) explained
Add up the implied chances of every outcome in a market and you get more than 100%. The extra is the bookmaker's built-in edge, called the overround. If both players in a tennis match are 1.91, each implies 52.4%, so the book adds up to about 104.7%. That works out to a margin of about 4.5% on your stakes: margin = 1 − 1 ÷ (sum of 1 ÷ odds). The second calculator does this for two- or three-way markets and shows the "fair" odds with the margin removed.
Lower margins mean more of your money comes back over time. Margins are usually lowest on big markets such as major football leagues and highest on niche markets and long accumulators.
Where to use it
Our top-rated site, 1win (9.9/10), has a full sportsbook and paid our crypto withdrawal in 15 minutes; use promo code Ultragambler. Compare more sportsbooks in our crypto betting sites and esports betting guides, or see cricket betting tips. Online betting isn't legal everywhere, so check the laws where you live first.
More free tools: the wagering requirement calculator shows what a bonus is really worth, and the gambling budget calculator helps you set limits before you play. Unsure about a term? See our gambling terms glossary.
Odds calculator FAQ
How do I calculate betting odds?
Convert the odds to decimal, then multiply by your stake to get the total return. For fractional odds a/b, the decimal is a ÷ b + 1; for American odds, see the conversion table above.
What does 6/4 mean in betting?
You win 6 for every 4 you stake, plus your stake back. In decimal that's 2.50, in American +150, and it implies a 40% chance.
What does −110 mean?
You must stake 110 to win 100 profit. That's decimal 1.91 or fractional 10/11, and it implies a 52.4% chance.
What are evens?
Evens (1/1, decimal 2.00, American +100) means you win the same amount as you stake. It implies a 50% chance.
Do higher odds mean a better bet?
Not on their own. Higher odds pay more because the outcome is less likely. A bet is only good value if its real chance of winning is higher than the chance the odds imply. Set a budget and only bet what you can afford to lose; our responsible gambling page has help if betting stops being fun.
