Probability Calculator
Calculate probability, odds in favor, odds against, and complementary probability from favorable and total outcomes.
Probability
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Probability (%) —
Odds In Favor —
Odds Against —
Complementary P (not event) —
How to Use This Calculator
Enter the number of Favorable Outcomes (how many ways the event can occur) and Total Outcomes (all possible outcomes). The calculator shows probability, percentage, odds for, odds against, and complementary probability.
Formula
P = Favorable / Total • Odds For = Favorable:Unfavorable • P(not A) = 1 − P(A)
Example
Drawing a red card from a deck: 26/52 = 0.5 = 50%, Odds 1:1
Frequently Asked Questions
- Probability measures how likely an event is to occur: P = favorable outcomes / total outcomes. Values range from 0 (impossible) to 1 (certain).
- Probability = favorable/(total). Odds = favorable:unfavorable. Example: P=1/4 means odds of 1:3.
- The probability that an event does NOT occur: P(not A) = 1 − P(A). If P(rain)=0.3, P(no rain)=0.7.
- Two events are independent if the outcome of one does not affect the other. For independent events, P(A and B) = P(A) × P(B).
- On a fair die: 1 favorable outcome, 6 total outcomes → P = 1/6 ≈ 0.1667 (16.67%). Odds: 1:5.