Fractional Odds Calculator: Profit, Returns and Conversion
The most common mistake is treating the numerator as the total return. Fractional odds quote profit. Decimal odds quote return including stake.
§ ON THIS PAGE · 9 sections
Convert fractional odds and calculate the return
Enter the numerator, denominator and stake. The result separates potential profit from total return.
- Decimal odds
- 3.50
- Implied probability
- 28.57%
- Indonesian odds
- +2.50
- Potential profit
- 25.00
- Total return
- 35.00
Decimal odds = numerator divided by denominator, plus one. Implied probability = 100 divided by decimal odds, before market margin.
How to read fractional odds
For odds A/B:
- A, the numerator, is the potential profit;
- B, the denominator, is the reference stake;
- the original stake is returned separately on a winning bet.
Betfair describes the notation directly:
“Fractional odds are numbers separated by a forward slash”
Return laboratory
Read the fraction as profit over stake
total return = stake + stake × (A / B)For decimal odds, divide A by B and add one. Fractional 7/4 therefore equals decimal 2.75.
Profit and total-return formulas
At fractional odds A/B:
profit = stake × (A / B)
total return = stake + profit
For a 20‑unit stake at 7/4:
profit = 20 × (7 / 4) = 35 units
total return = 20 + 35 = 55 units
| Fraction | Profit on 10 units | Total return | Decimal |
|---|---|---|---|
| 1/4 | 2.50 units | 12.50 units | 1.25 |
| 1/1 | 10.00 units | 20.00 units | 2.00 |
| 7/4 | 17.50 units | 27.50 units | 2.75 |
| 5/1 | 50.00 units | 60.00 units | 6.00 |
- Profit on 10 units
- 2.50 units
- Total return
- 12.50 units
- Decimal
- 1.25
- Profit on 10 units
- 10.00 units
- Total return
- 20.00 units
- Decimal
- 2.00
- Profit on 10 units
- 17.50 units
- Total return
- 27.50 units
- Decimal
- 2.75
- Profit on 10 units
- 50.00 units
- Total return
- 60.00 units
- Decimal
- 6.00
Convert fractional odds to decimal and American
Fractional to decimal:
decimal odds = (A / B) + 1
So 11/4 becomes:
(11 / 4) + 1 = 3.75
The calculator also shows Indonesian odds. For decimal prices of 2.00 or higher, a positive Indonesian number is profit per unit staked: decimal 2.50 is Indonesian +1.50. Below decimal 2.00, the number is negative and shows the stake needed to win one unit: decimal 1.50 is Indonesian -2.00, or 0.50 units profit per unit staked. The sign changes the display, not the underlying price.
To convert a positive decimal price into fractional form:
- subtract one;
- express the remaining number as a reduced fraction.
For example, 3.75 - 1 = 2.75 = 11/4.
American conversion has two branches:
- fractional odds at evens or longer:
+100 × (A/B); - odds‑on fractions:
-100 × (B/A).
Thus 5/2 is +250, while 1/4 is ‑400.
Calculate implied probability
For fractional odds A/B:
implied probability = B / (A + B)
At 5/2:
2 / (5 + 2) = 28.57%
This is the break-even probability before considering market margin. It is not proof that the event actually has a 28.57% chance. The bookmaker-margin guide explains why all displayed probabilities in a market can add to more than 100%.
Odds-on, evens and odds-against
| Label | Fraction shape | Profit relative to stake |
|---|---|---|
| Odds-on | Numerator smaller than denominator, such as 1/4. | Potential profit is smaller than the stake. |
| Evens | 1/1, also shown as EVS. | Potential profit equals the stake. |
| Odds-against | Numerator larger than denominator, such as 5/2. | Potential profit is larger than the stake. |
- Fraction shape
- Numerator smaller than denominator, such as 1/4.
- Profit relative to stake
- Potential profit is smaller than the stake.
- Fraction shape
- 1/1, also shown as EVS.
- Profit relative to stake
- Potential profit equals the stake.
- Fraction shape
- Numerator larger than denominator, such as 5/2.
- Profit relative to stake
- Potential profit is larger than the stake.
Price comparison checklist
- Convert every price to the same format.
- Compare total return, not the visual size of the fraction.
- Keep more decimal precision than the interface displays.
- Calculate implied probability.
- Check whether commission or a promotion changes the return.
- Save the accepted price rather than the earlier quoted price.
Understanding a price does not reduce the event's uncertainty. Keep stakes inside a fixed loss limit and do not interpret a short fraction as certainty. The value, ROI and risk guide explains why a correctly converted price is only the input to an edge calculation, not evidence that the selection is profitable.
Find the cost hidden across the whole market
Convert every outcome to implied probability, add them and separate the quoted market percentage from a fair 100% book.
Update record, 21 August 2026: surfaced the converter in the title and added worked positive and negative Indonesian‑odds examples.
FAQ
What do fractional odds of 5/2 mean?
They mean 5 units potential profit for every 2 units staked. A winning 2-unit bet returns 7 units because the stake is also returned.
How do I convert fractional odds to decimal?
Divide the numerator by the denominator and add one. For example, 5/2 becomes 2.5 plus 1, which is 3.50.
How do I calculate implied probability from fractional odds?
Divide the denominator by the sum of the numerator and denominator. For 5/2, the calculation is 2 divided by 7, or 28.57%.
What does odds-on mean?
The potential profit is smaller than the stake. A fraction such as 1/4 is odds-on and equals 1.25 decimal.
Are fractional odds worse than decimal odds?
No. They are different displays of the same price. Decimal odds make total return easier to multiply, while fractions show profit relative to stake.
Evidence manifest3 primary sources mapped to this guideView sources
Each source below is retained with the claims it supports. Operator sources describe published terms, not independent first‑hand performance.
- Betfair odds calculation guide (opens in a new tab)
- Fractional odds are numbers separated by a forward slash
- Using the number to the right of the fractional odds, divide it by the total of both the numbers in the fractional odds, and then multiply by 100
- Smarkets implied-probability guide (opens in a new tab)
- Odds in any format are a different display of the same chance
- Fractional implied probability is denominator divided by denominator plus numerator
- The Jockey Club racing jargon guide (opens in a new tab)
- Odds-on fractional prices have the larger number on the bottom of the fraction
- Evens means a profit of 1 for every 1 bet