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Probability calculator

Calculate event probabilities, recover independent probabilities from two known values, or use a normal interval.

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  1. Use the example values or enter your own measurements.
  2. Calculate, then copy the result or download the available details.

Example

Input

Independent events A = 0.31, B = 0.56

Expected result

At least one: 0.6964

Try it

Good to know

The calculation runs in your browser. Use consistent units in fields with no explicit unit.

Calculation method

Independent events satisfy P(A∩B)=P(A)P(B). For dependent events, enter the intersection directly. Repeated trials multiply their probabilities, and the probability of at least one success uses the complement.

P(A∪B)=P(A)+P(B)−P(A∩B)P(A\cup B)=P(A)+P(B)-P(A\cap B)
P(A∩B)=P(A)P(B)(independent)P(A\cap B)=P(A)P(B)\quad\text{(independent)}

Calculation mode

Two independent events
  • Probability of A
  • Probability of B
Known intersection
  • Probability of A
  • Probability of B
  • Both events
Recover independent events
  • First known quantity · Probability of A / Probability of B / Not A / Not B / Both events / At least one event / Exactly one event / Neither event
  • First probability
  • Second known quantity · Probability of A / Probability of B / Not A / Not B / Both events / At least one event / Exactly one event / Neither event
  • Second probability
Repeated independent trials
  • Probability of A
  • Trials of A
  • Probability of B
  • Trials of B
Normal distribution interval
  • Mean
  • Standard deviation
  • Lower bound
  • Upper bound