Odds Converter
Odds Converter: American, Decimal and Fractional Odds in One Click
The odds converter takes a number in any one field and fills in the other formats instantly. US sportsbooks show American odds (-110, +150); decimal odds (1.91) include the stake and are used by most calculators; fractional odds (10/11) are the UK convention. The conversions: for decimal odds of 2.00 or more, American = (decimal − 1) × 100; below 2.00, American = −100 ÷ (decimal − 1); fractional = decimal − 1 reduced to a fraction; implied probability = 1 ÷ decimal.
Odds Converter
Odds ConverterConvert American, decimal and fractional odds and implied probability
American (plus) = (decimal − 1) × 100 when decimal ≥ 2; American (minus) = −100 ÷ (decimal − 1) when decimal < 2Decimal = 1 + numerator ÷ denominator; implied probability = 1 ÷ decimal.
How to use the odds converter
Fill in any one of the four fields and the other three update. Every other calculator on this site takes decimal odds, so the typical workflow is: read the American price off your sportsbook, convert it here, then paste the decimal value into the parlay, Kelly or expected value calculator.
American odds work on a base of 100. A minus number is the favorite and shows how much you risk to win $100: at -110 you risk $110 to win $100. A plus number is the underdog and shows the profit on a $100 stake: +150 wins $150. Decimal odds instead show the total return per $1 staked, so -110 becomes 1.91 and +150 becomes 2.50.
The implied probability field also works backwards. If you make a team a 60% winner, enter 60 and the converter returns fair odds of -150 (1.67). Any sportsbook price longer than that, such as -140, is a side with value.
How to read the three odds formats
Decimal odds are the most direct: payout = stake × odds. 2.00 is a coin flip; below 2.00 is a favorite, above 2.00 an underdog.
American odds use 100 as the reference: +150 means a $100 bet wins $150, -110 means you bet $110 to win $100. The bigger the minus number, the heavier the favorite. +100 (even money) equals decimal 2.00.
Fractional odds give profit relative to stake: 3/2 means win $3 for every $2 staked, decimal 2.50 or +150; 1/4 means win $1 for every $4 staked, decimal 1.25 or -400.
Example: converting the standard -110 spread price
- -110 is a minus price: decimal = 1 + 100 ÷ 110 = 1.909, shown as 1.91.
- Fractional: 0.909 = 10/11.
- Implied probability: 1 ÷ 1.909 = 52.4%; with both sides at -110 the two sides total 104.76%.
When a sportsbook lists the Chiefs -3.5 at -110, that is 1.91 in decimal and the market rates the cover at 52.4% including vig. Going the other way, a +150 underdog is decimal 2.50, fractional 3/2 and a 40% implied probability.
FAQ
What are American odds?+
The format US sportsbooks use. A minus number is the favorite and shows the amount you risk to win $100 (-110 risks $110); a plus number is the underdog and shows the profit on $100 (+150 wins $150). Even money is +100.
What is -110 in decimal odds?+
-110 = 1 + 100 ÷ 110 = 1.909, usually shown as 1.91, an implied probability of 52.4%. It is the standard price on both sides of NFL, NBA and MLB spreads and totals, and it builds in a 4.76% vig.
What is 5/2 in decimal and American odds?+
5/2 = 1 + 2.5 = decimal 3.50, which is +250 in American odds, with an implied probability of 28.6%. Fractional odds are profit over stake, so 5/2 means win $5 for every $2 risked.
Can I convert a win probability back into odds?+
Yes. Fair decimal odds = 1 ÷ probability, so 60% is 1.67 (-150) and 40% is 2.50 (+150). Enter the percentage in the implied probability field and the converter shows the matching American, decimal and fractional odds.
Why do decimal odds include the stake?+
Decimal odds give the total return per unit staked, so payout is simply stake times odds, which makes parlay and Kelly math easier. American and fractional odds express profit only, so add the stake back when converting to decimal.
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Open calculator →Done calculating? See how the AI reads today’s games
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For informational purposes only. Sports betting is legal in 39 states and D.C.; rules and minimum age vary by state. 21+. Gambling problem? Call 1-800-GAMBLER.
Odds and vig conventions follow standard US sportsbook pricing (-110 on spreads and totals). The tax line is based on IRS Topic 419 and the Form W-2G instructions (rev. 01/2026); it is not tax advice.