Compute Probability Calculator

A probability between 0 and 1. Enter 0.25, not 25.
Leave blank for single-event questions.
Optional. Supply this when the events are not independent; it overrides the independence assumption.
Optional. Used to derive the joint probability and, with Bayes, to invert to P(B|A).
Each repetition has probability A of occurring.
The values a discrete random variable can take.
One probability per outcome value. They must add up to 1.
P(not A)
0.5
Probability Calculator
Odds for A (X to 1)
1
Odds against A (X to 1)
1
P(A never happens)
0.5
P(A happens at least once)
0.5
P(A happens every time)
0.5
Independence
Only one event was given.
Worked out from Kolmogorov axioms and the addition rule: P(A or B) = P(A) + P(B) - P(A and B) and 3 other sources.

How this is worked out

1 step
  1. P(not A) = 1 - 0.5 = 0.5.

Results are general information, not financial, tax, legal, medical or engineering advice.