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Betting Odds Calculator: Decimal, Fractional, US
Convert common betting-odds formats and calculate implied win probability, stake returns and hypothetical expected value. This calculator does not place bets.
How it works & examplesUnderstand the calculation
Convert betting odds without mistaking price for probability
Decimal, fractional and American odds can express the same payout. Decimal odds of 2.50 correspond to fractional 3/2 and American +150. A stake of 10 returns 25 gross if it wins, leaving 15 profit. Dividing one by 2.50 gives a 40% break-even probability before fees.
Implied probability still includes the bookmaker's margin when you compare a whole market; separate it with Vig Calculator: Overround and No-Vig Odds.
That 40% is the probability implied by the price, not an independently verified forecast. To evaluate a wager, compare the price with your own probability assumption. To measure the bookmaker margin, enter all mutually exclusive outcomes into the Vig calculator rather than judging a market from one quoted selection.
Maths & verification
Convert decimal, American and fractional odds, calculate implied probability, potential return, net profit and expected value for a given stake.
Try the simulator below. Input values stay in your browser; no account or money is involved.
Model assumptions: No. Virtual games use declared teaching models. Verify any actual operator’s payout rules independently.
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How to use the tool
Convert sportsbook-style decimal, fractional and American odds and separate price-implied probability from your own estimate.
- Choose the odds format and enter the quoted price.
- Enter a hypothetical stake and your own estimated win probability.
- Compare equivalent formats, gross return, net profit, break-even probability and expected value.
Understanding your result
Decimal odds 2.50 equal 3/2 or +150 and imply 1/2.50 = 40% break-even probability before adjusting for bookmaker margin. A 100-unit stake would return 250 gross on success.
Scope and limitations
This single-outcome converter does not calculate dutching, accumulators, surebets or overround across an entire market. Those require multiple prices and a different calculator.
Before you rely on the result
- How the calculation works
Formulas, assumptions, rounding and model limits are documented on the methodology page.
- Check the current inputs
Use the odds, RTP, fees, bonus terms or other values currently shown by the operator or market.
Betting odds conversion: implied probability, payout and break-even
Odds conversion is useful because decimal, fractional and American formats describe the same price in different notation. The key number underneath them is implied probability.
For decimal odds d, implied probability = 1 / d. Gross return = stake × d, and net profit = stake × (d − 1). The break-even probability is the implied probability before any adjustment for bookmaker margin.
The same price in three common formats
Decimal 2.50, fractional 3/2 and American +150 all represent the same payout relationship and a 40% implied probability.
| Decimal | Fractional | American | Implied probability |
|---|---|---|---|
| 1.50 | 1/2 | −200 | 66.67% |
| 2.00 | 1/1 | +100 | 50.00% |
| 2.50 | 3/2 | +150 | 40.00% |
| 3.00 | 2/1 | +200 | 33.33% |
| 4.00 | 3/1 | +300 | 25.00% |
Implied probability is not automatically the true probability
A bookmaker can include margin in its prices, so a single line's implied probability is only the break-even rate for that price. To estimate a no-vig probability you need every mutually exclusive outcome in the same market.
Payout versus profit
At decimal odds 2.50, a 100-unit winning stake returns 250 gross and 150 net profit. Confusing gross return with profit is one of the most common odds-calculator mistakes.
Worked example
Decimal odds 2.50 equal fractional odds 3/2 and American odds +150. They imply 1/2.50 = 40% before considering margin. A hypothetical 100-unit stake yields 250 gross and 150 net profit if it wins.
Does 40% implied probability mean a 40% true win chance?
Not necessarily. It is derived from the quoted price; your own probability estimate may differ and bookmaker margins may be included.
Questions about this calculation
What is the difference between implied and true probability?
Implied probability is a mathematical conversion of a quoted price; true win probability is unknown and may differ after accounting for margin.
Does positive expected value guarantee a profit?
No. The calculated EV uses the probability you supplied and describes a long-run mathematical expectation, not the result of an individual bet.
When is Betting Odds Calculator: Decimal, Fractional, US the right tool?
Convert sportsbook-style decimal, fractional and American odds and separate price-implied probability from your own estimate.
How should I read the result from Betting Odds Calculator: Decimal, Fractional, US?
Decimal odds 2.50 equal 3/2 or +150 and imply 1/2.50 = 40% break-even probability before adjusting for bookmaker margin. A 100-unit stake would return 250 gross on success.
What can Betting Odds Calculator: Decimal, Fractional, US not tell me?
This single-outcome converter does not calculate dutching, accumulators, surebets or overround across an entire market. Those require multiple prices and a different calculator.