Fractional odds, without the guesswork.
OddsCalculator.ca
Fractional odds show profit relative to stake. The numerator is potential profit; the denominator is the stake unit. The original stake is returned separately on a win.
How to read 5/2 and 3/2
At 5/2, each $2 staked earns $5 profit if successful. A $100 stake therefore earns $250 profit and returns $350. At 3/2, $100 earns $150 profit and returns $250.
Use profit = stake × numerator ÷ denominator. Add the original stake for total payout. Both numbers in the fraction must be positive, and the denominator must never be zero.
Odds-on prices and reduced fractions
A fraction below 1 describes less profit than the stake. At 1/2, a $100 stake earns $50 and returns $150. This is equivalent to −200 American or 1.50 decimal.
Fractions such as 6/4 and 3/2 describe the same price. Dividing the numerator and denominator by their greatest common divisor reduces the fraction without changing its value.
Conversion and precision policy
The calculator keeps the original price for calculations. When feasible, it retains an exact ratio from the numbers you entered, so decimal 1.0001 becomes 1/10000 and decimal 1.00001 becomes 1/100000. Ordinary prices still work as expected: 2.50 becomes 3/2, and fractional 6/4 reduces to 3/2.
Exact ratios are displayed without an approximation sign. If the reduced ratio is too large, a continued-fraction search tries up to 64 steps, with both numerator and denominator limited to one trillion. An approximate result must be within 0.000001% (relative error 1e−8) of the original profit ratio. Approximations are marked ≈. If that accuracy is not possible within the limits, the output says “Precision limit — use decimal odds” instead of displaying a misleading fraction.
For a calculated price without an original entered ratio, a fraction that matches within floating-point arithmetic tolerance may appear without ≈; this indicates numerical agreement, not a proof of mathematical equality. Fair odds use an exact ratio derived from your entered probability where feasible.
Money normally displays two decimal places, decimal odds four and probability two. Extra precision is used near a boundary. A positive profit below one cent is shown as <$0.01, and a probability below 100% is never displayed as exactly 100%. Returned fractions and display rounding never replace the original calculation price.
Keep the original price when comparing
Changing formats converts the same price. For example, −200 becomes decimal 1.50 and fractional 1/2. Switching back and forth does not repeatedly round the underlying value. Stakes and independent inputs are preserved.
If an accurate fraction is unavailable or only approximate, the calculator keeps the original price and explains the limitation. Editing the converted input replaces the price with the new entry. Incomplete input is left for you to finish; changing formats does not load an unrelated example.
Explore the numbers
Use the calculators to try these examples with your own inputs. Calculations describe prices and conditional returns, not guaranteed outcomes.
Convert odds and calculate payout
Swipe or scroll to see all columns →
| Odds | Net profit | Total payout | Implied probability |
|---|---|---|---|
| +150 | $150.00 | $250.00 | 40.00% |
| −200 | $50.00 | $150.00 | 66.67% |
| −110 | $90.91 | $190.91 | 52.38% |
| 2.50 decimal | $150.00 | $250.00 | 40.00% |
| 3/2 fractional | $150.00 | $250.00 | 40.00% |
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