Probability Calculator
Calculate the probability of a single event from favorable and total outcomes. Get the result as a fraction, decimal, percentage and odds.
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Save ⟶How to use the Probability Calculator
- 1Enter favorable outcomes in the form on the left.
- 2Fill in the remaining fields — the result updates automatically as you type.
- 3Review the highlighted result and the supporting breakdown on the right.
- 4Use Copy, Share or Print to save or send your result.
Probability vs. odds
Probability is favorable outcomes divided by total outcomes: drawing a heart from a deck is 13/52 = 0.25 = 25%. Odds compare favorable to unfavorable outcomes: the same event has odds of 13 to 39, or 1:3. Bookmakers and statistics both use odds, so knowing the conversion avoids confusion.
For independent events, multiply probabilities (two coin heads in a row: 0.5 × 0.5 = 0.25). For mutually exclusive events, add them.
Frequently Asked Questions
▸How do I convert odds to probability?
Odds of a:b in favor means probability = a/(a+b). Odds of 1:3 = 1/4 = 25% probability.
▸Can probability be greater than 1?
No — probability ranges from 0 (impossible) to 1 (certain). Anything above 1 indicates a calculation error.