How to use the odds converter
The converter turns one price into the two other formats and gives the implied probability behind it. It takes three steps:
- Pick the format of the odds you have: decimal (2.50), fractional (6/4) or American (+150).
- Type the price. Decimal odds take a point or a comma. Fractions can be written 5/2 or 5-2, and “evens” works too. American odds take a plus or a minus sign: +150, −200.
- Read the result. The two other formats appear next to the implied probability, with a sentence saying what that percentage means for this price.
Switching the format converts what you already typed, so you can go back and forth without retyping. Try 11/10 in fractional: you get 2.10 in decimal, +110 in American and an implied probability of 47.6%.
The conversion formulas
Decimal odds include your stake: 2.50 means $2.50 back for every $1 staked. Fractional and American odds show the profit instead, which is why every formula below adds or removes 1.
Fractional to decimal = 1 + numerator ÷ denominator
Positive American to decimal = 1 + American ÷ 100
Negative American to decimal = 1 + 100 ÷ |American|
Implied probability = 1 ÷ decimal odds
So 5/2 becomes 1 + 2.5 = 3.50, +250 becomes 1 + 2.5 = 3.50 too, and −200 becomes 1 + 0.5 = 1.50. Going the other way, a decimal price of 2.00 or more becomes a positive American line ((decimal − 1) × 100), and a price under 2.00 becomes a negative one (−100 ÷ (decimal − 1)).
Common fractional odds, converted
British bookmakers and racing coverage still quote fractions. These are the prices you meet most often, from odds-on favourites to long shots.
| Fractional | Decimal | American | Implied probability |
|---|---|---|---|
| 4/6 | 1.67 | −150 | 60.0% |
| 4/5 | 1.80 | −125 | 55.6% |
| Evens (1/1) | 2.00 | +100 | 50.0% |
| 11/10 | 2.10 | +110 | 47.6% |
| 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% |
| 4/1 | 5.00 | +400 | 20.0% |
| 5/1 | 6.00 | +500 | 16.7% |
| 10/1 | 11.00 | +1000 | 9.1% |
Anything shorter than evens is “odds-on”: the fraction is smaller than 1, the American line is negative, and the implied probability is above 50%.
What the implied probability tells you, and what it does not
The implied probability is the chance the price stands for, and also the share of bets at that price you would need to win just to break even. At 2.10, that is 47.6%: win fewer than about 48 bets in 100 at those odds and you lose money.
It is not the true chance of the outcome. Each price carries part of the bookmaker’s margin, so the implied probabilities of all the outcomes of a market add up to more than 100%. To see that margin and the fair probabilities without it, enter the whole market in the bookmaker margin calculator. For the reasoning behind all this, read our guide to implied probability.
The same logic applies to a parlay: its odds are the product of the odds of each leg, and its implied probability the product of theirs. The bet calculator works that out for you, voids and losing legs included.
Common conversion mistakes
- Forgetting the stake with fractions. $10 at 6/4 returns $25: $15 of profit plus the $10 staked. The decimal price, 2.50, gives the full return directly.
- Reading the minus sign the wrong way. −150 is a favourite: you stake $150 to make $100. +150 is an underdog: $100 makes $150.
- Trusting rounded prices to the last decimal. 10/11 is 1.909…, which bookmakers show as 1.91. The tiny gap matters little on one bet, but it adds up if you rebuild your stats by hand.
- Taking the percentage for a forecast. A price moves with the money placed on it and with news. It is what the bookmaker charges, not what will happen.
Frequently asked questions
How do I convert fractional odds to decimal?
Divide the first number by the second and add 1. 5/2 is 2.5 + 1 = 3.50, and 4/6 is 0.67 + 1 = 1.67. Decimal odds include the stake, which is why the 1 is added.
How do I convert American odds to decimal?
For a positive line, divide by 100 and add 1: +150 becomes 2.50. For a negative line, divide 100 by the number and add 1: −200 becomes 1.50.
What does “evens” mean in betting?
Evens is 1/1: you win as much as you stake. It is 2.00 in decimal, +100 in American, and an implied probability of 50%.
Does the implied probability include the bookmaker’s margin?
Yes. It is the chance the price stands for, margin included, so the true chance is usually a little lower. The margin calculator removes it once you enter every outcome of the market.
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