Probability Calculator
Free online probability calculator. Calculate the probability of multiple independent events happening, including P(A and B), P(A or B), and neither.
Probability Calculator
A and B occurs: P(A ∩ B)25%Decimal: 0.25
A or B occurs: P(A ∪ B)75%Decimal: 0.75
Exactly one occurs50%Decimal: 0.5
Neither occurs: P(A' ∩ B')25%Decimal: 0.25
A does not occur: P(A')50%
B does not occur: P(B')50%
* Assuming Event A and Event B are statistically independent events.
How to Calculate Probability?
Probability is a measure of 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.
Independent Events
This calculator assumes that Event A and Event B are independent. Two events are independent if the occurrence of one does not affect the probability of occurrence of the other (e.g., flipping two different coins).
Key Probability Formulas
- Probability of A NOT occurring P(A'):
1 - P(A) - Probability of A AND B occurring P(A ∩ B):
P(A) × P(B) - Probability of A OR B occurring P(A ∪ B):
P(A) + P(B) - P(A ∩ B) - Probability of NEITHER occurring P(A' ∩ B'):
(1 - P(A)) × (1 - P(B)) - Probability of EXACTLY ONE occurring:
P(A) × P(B') + P(A') × P(B)