Odds to Probability Calculator
Implied probability from odds, in decimal and fractional form, with the return on a stake.
Results
Probability
75.00000
%
Decimal odds
1.33333
Fractional odds (against)
0.33333
Total return
13.333
Profit
3.333
What this tool does
Odds of 3 to 1 on mean a 75 percent chance, while 3 to 1 against mean 25 — the direction matters as much as the numbers, and confusing the two is how people misread a form guide. Note that bookmakers' odds always imply probabilities adding to more than 100 percent across a field; the difference is their margin, not a mistake.
Formula
p = a ÷ (a + b) ; share decimal = 1 ÷ p
Variables
| Symbol | Meaning | Unit |
|---|---|---|
oa | Odds in favour | — |
ob | Odds against | — |
st | Stake | — |
PR | Probability | % |
DE | Decimal odds | — |
FR | Fractional odds (against) | — |
RT | Total return | — |
PF | Profit | — |
Worked example
- Odds in favour3
- Odds against1
- Stake10
- Probability75.00000 %
- Decimal odds1.33333
- Fractional odds (against)0.33333
- Total return13.333
- Profit3.333
Limitations
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.
- This is an informational calculator, not personalised financial advice. Rates, fees, taxes and contract conditions vary between institutions and countries.