The same price written three ways, what each one means, how to convert between them and how to see the probability, and the margin, hidden inside.
A bookmaker in London writes 6/4, one in Milan writes 2.50 and one in New Jersey writes +150. They are quoting the same thing: stake 100 and, if you win, receive 250 back, 150 of it profit. The formats differ only in what they count.
| Format | Example | What it shows | Return on 100 |
|---|---|---|---|
| Decimal | 2.50 | Total return per unit staked, stake included | 250 |
| Fractional | 6/4 | Profit per unit staked: 6 won for every 4 staked | 250 |
| American, positive | +150 | Profit on a 100 stake | 250 |
| American, negative | -200 | Stake needed to win 100 profit | 150 |
Fractional to decimal: divide the fraction and add 1, so 6/4 is 1.5 + 1 = 2.50, and 1/5 is 0.2 + 1 = 1.20. American to decimal: for a positive number divide by 100 and add 1, so +150 is 2.50; for a negative number divide 100 by the number and add 1, so -200 is 100/200 + 1 = 1.50. Decimal to American: for odds above 2.00, subtract 1 and multiply by 100; below 2.00, divide -100 by the odds minus 1.
Divide 1 by the decimal odds and you have the implied probability. Odds of 2.50 imply 40 percent; 1.40 implies 71.4 percent; 6.00 implies 16.7 percent. This is the number that matters when you compare your own view with the bookmaker’s: if you think a team wins more often than the price implies, the bet has value; if not, it does not, whatever the odds look like.
Add the implied probabilities of every outcome in a market. In a fair market they would sum to 100 percent. At a bookmaker they sum to more, and the excess is the margin. A football match at 2.10, 3.40 and 3.60 implies 47.6 + 29.4 + 27.8 = 104.8 percent: the bookmaker is keeping 4.8 percent of the money staked on that market, on average, whatever happens. Our page on the bookmaker’s margin shows what that costs over a season.
Decimal, always, for comparing prices: it makes the arithmetic trivial and every serious odds comparison tool uses it. Switch the display in your account settings; every bookmaker in our ranking allows it, including the American ones.
Odds of 2.00, 1/1 or +100: the profit equals the stake.
None; the format is presentation. The price is the price.
A negative number shows the favourite: the amount you must stake to win 100.