Probability Calculator
Use this probability calculator to calculate the chance of an event or outcome. Enter the known outcomes, events or probabilities requested by the tool and review a probability, odds or percentage chance.
P(A and B)
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P(A or B) —
P(not A) —
P(neither) —
Assumes A and B are independent events.
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How it works
P(A and B) = P(A)·P(B); P(A or B) = P(A)+P(B)−P(A and B); P(not A) = 1−P(A)How to use the Probability Calculator
Start by entering the known outcomes, events or probabilities requested by the tool. Keep the units consistent and check that each value belongs to the same question.
The result gives a probability, odds or percentage chance. The result depends on the assumptions and whether events are independent. Use it as a guide and check any instructions, rules or professional advice that apply.
Frequently Asked Questions
What does this probability calculator calculate?
It gives a probability, odds or percentage chance. The result depends on the assumptions and whether events are independent.
What information should I enter?
Enter the known outcomes, events or probabilities requested by the tool. Use the same units throughout so the result is easier to understand.
Can probability guarantee what will happen?
No. It describes likelihood, not certainty.