This free odds calculator converts between fractional odds, decimal odds, American odds, and implied probability. Whether you’re betting, studying statistics, or working with probabilities, the calculator makes it easy to switch between formats and understand the true chance of an event.
In mathematics and betting, odds express the ratio of success to failure. Unlike probability (which is success ÷ total outcomes), odds compare success vs failure directly.
Example: For a coin toss,
Probability of heads = 0.5 (50%)
Odds for heads = 1:1 (one favourable vs one unfavourable)
The calculator also shows implied probability, which helps you understand the true chance behind betting odds.
$$ P = \frac{\text{Odds (for)}}{\text{Odds (for)} + \text{Odds (against)}} $$
Odds of 2:3 → $$ P = \frac{2}{2+3} = \frac{2}{5} = 0.4 = 40\% $$
Fractional to Probability:
5/2 odds → P = 5 ÷ (5+2) = 71.4%
Decimal to Probability:
2.5 odds → P = 1 ÷ 2.5 = 40%
American to Probability:
+150 odds → P = 100 ÷ (150+100) = 40%
-200 odds → P = 200 ÷ (200+100) = 66.7%
Q: Are odds and probability the same?
A: No. Probability is success ÷ total outcomes. Odds compare success vs failure.
Q: How do you convert odds to probability?
A: Use the formula P=A÷(A+B)P = A ÷ (A + B) where A:B are odds.
Q: Which odds format is best?
A: Depends on region. UK uses fractional, Europe uses decimal, US uses American.
Q: What does “implied probability” mean?
A: It’s the hidden chance behind any odds format, showing the real likelihood of the event.