Probability Calculator
Calculate the probability of single and multiple events. Determine the odds of favorable outcomes, unions (A or B), and intersections (A and B).
The number of ways the event can occur.
Total number of possible results.
About Probability
Probability measures the likelihood that an event will occur. It is quantified as a number between 0 and 1, where 0 indicates impossibility and 1 indicates certainty.
Single Event Formula
The probability of a single event $A$ is calculated by dividing the number of favorable outcomes by the total number of possible outcomes.
P(A) = Favorable / Total
Multiple Events (Independent)
When two events $A$ and $B$ are independent (the outcome of one does not affect the other):
- Intersection (A and B): $P(A \cap B) = P(A) \times P(B)$
- Union (A or B): $P(A \cup B) = P(A) + P(B) - P(A \cap B)$
- Complement (Not A): $P(A') = 1 - P(A)$
? Frequently Asked Questions
Events are independent if the occurrence of one does not affect the probability of the other occurring (e.g., rolling a die twice). If events are dependent (e.g., drawing cards from a deck without replacement), the formulas used here do not apply directly.
Probability is the ratio of favorable outcomes to the *total* number of outcomes. Odds are the ratio of favorable outcomes to *unfavorable* outcomes.
No. Probability is always expressed as a value between 0 (0%) and 1 (100%).