ODDS CONVERTER
Type a price in decimal, fractional or American format and the other two appear instantly, together with the implied probability: the win rate at which the bet breaks even. Add the price of the other side of a two-way market and the converter also strips out the bookmaker’s margin to show the fair odds.
Pure arithmetic, no odds feed — see our methodology · Last updated
Type in any one field; the other formats update as you type.
Each row is one price written three ways, with the win rate it needs to break even.
| Decimal | Fractional | American | Implied probability |
|---|---|---|---|
| 1.25 | 1/4 | −400 | 80.0% |
| 1.50 | 1/2 | −200 | 66.7% |
| 1.80 | 4/5 | −125 | 55.6% |
| 1.91 | 10/11 (exactly 1.909) | −110 | 52.4% |
| 2.00 | 1/1 (evens) | +100 | 50.0% |
| 2.20 | 6/5 | +120 | 45.5% |
| 2.50 | 6/4 (3/2) | +150 | 40.0% |
| 3.00 | 2/1 | +200 | 33.3% |
| 4.00 | 3/1 | +300 | 25.0% |
| 6.00 | 5/1 | +500 | 16.7% |
| 11.00 | 10/1 | +1000 | 9.1% |
Not sure which to choose? See what we recommend for each type of player.
Three ways of writing one price
Decimal odds, standard across Europe, Australia and almost every crypto sportsbook, give the total return per unit staked: 2.50 returns 2.50 for every 1 bet, stake included. Fractional odds, the UK and Irish convention, give the profit relative to the stake: 6/4 pays 6 for every 4 staked. American odds pivot on 100: a plus number is the profit on a 100 stake, a minus number is what you must stake to win 100. Decimal 2.50, fractional 6/4 and American +150 are the same bet.
The conversion formulas
Everything runs through the decimal price d. From fractional a/b: d = 1 + a/b. From American +A: d = 1 + A/100; from −A: d = 1 + 100/A. Back the other way, fractional is d − 1 reduced to a simple fraction, and American is +(d − 1) × 100 when d ≥ 2 or −100 / (d − 1) when it is below 2. Implied probability is 1 / d. The converter rounds fractional output to the nearest fraction with a denominator up to 100, which is why 1.91 shows as 91/100 rather than the 10/11 (1.909) that bookmakers quote.
Removing the margin: no-vig fair odds
Add up the implied probabilities of every outcome in a market and the total comes to more than 100%. The excess is the bookmaker’s margin, also called the overround or vig. A tennis match priced 1.91 / 1.91 sums to 52.4% + 52.4% = 104.7%, so the book keeps about 4.5% of the money staked on both sides. To recover the fair price, divide each side’s implied probability by the total and invert: 52.4% ÷ 1.047 = 50%, which is fair odds of 2.00 for each player.
This proportional method spreads the margin evenly across the outcomes. Books often load more of it onto the longshot, so on lopsided markets the fair price of the favourite can be slightly shorter than this method shows. For three-way football markets, use the margin calculator, which handles 1X2 prices.
Using implied probability
Implied probability is the break-even win rate. A bettor who takes prices around 1.91 needs to win 52.4% of bets just to stand still, and one taking 2.50 needs 40%. If your own estimate of a selection’s chance is higher than the implied probability, the price may be value; if it is lower, the bet loses money over time, whatever the format. To size a bet you believe has an edge, take the decimal price to the Kelly criterion calculator, where the net odds are the decimal price minus 1.
Related Tools
Betting maths: Bookmaker Margin Calculator · Kelly Criterion Calculator · House Edge Calculator
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Check the house before the price: provably fair sportsbooks