Probability Calculator

Calculate probability of events and combined probabilities.

Favorable Outcomes

Total Outcomes

Event 2 Favorable (for combined)

Event 2 Total

Results

P(Event 1)0.3

P(Event 2)0.4

P(E1 AND E2)0.12

P(E1 OR E2)0.58

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What is Probability?

Probability measures how likely an event is to occur, expressed as a number between 0 (impossible) and 1 (certain). It's fundamental to statistics, gambling, insurance, weather forecasting, and decision-making.

Formula

P(Event) = Favorable Outcomes / Total Outcomes P(A AND B) = P(A) × P(B) (independent events) P(A OR B) = P(A) + P(B) − P(A AND B) P(NOT A) = 1 − P(A)

How to use this Probability Calculator?

1. Enter favorable and total outcomes for Event 1. 2. Enter the same for Event 2 (for combined probability). 3. See individual and combined probabilities.

Frequently asked questions

What is the probability of rolling a 6?

P(6) = 1/6 = 0.1667 = 16.67%. A fair die has 6 equally likely outcomes.

What is the probability of heads twice in a row?

P(HH) = 1/2 × 1/2 = 1/4 = 0.25 = 25%. Each flip is independent.

What is Bayes' theorem?

Bayes' theorem calculates conditional probability: P(A|B) = P(B|A) × P(A) / P(B). It's used in medical testing, spam filters, and machine learning.

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