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Probability Calculator
Probability
0%
Fraction
0/1
Decimal
0
Odds
0:1
Assumes independent events
A AND B (both occur) 0%
A OR B (either occurs) 0%
NOT A (A doesn't occur) 0%
NOT B (B doesn't occur) 0%
Percentage
—
Decimal
—
Fraction
—
Odds
—
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How to Use the Calculator
- Single Event: Enter favorable and total outcomes
- Combined: Enter two probabilities to find AND/OR
- Convert: Convert between %, decimal, fraction, odds
Probability Formulas
- P(A and B) = P(A) × P(B) for independent events
- P(A or B) = P(A) + P(B) - P(A and B)
- P(not A) = 1 - P(A)
- Odds = P(success) : P(failure)
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Frequently Asked Questions
What is probability?
Probability measures the likelihood of an event occurring, expressed as a number between 0 (impossible) and 1 (certain), or as a percentage (0% to 100%).
How do I calculate probability?
Basic probability = Number of favorable outcomes ÷ Total possible outcomes. For example, rolling a 6 on a die: 1/6 ≈ 16.67%.
What are odds vs probability?
Probability is successes/total. Odds are successes/failures. 1/4 probability = 1:3 odds (1 success for every 3 failures).
What is independent probability?
Independent events don't affect each other. Multiply their probabilities. Example: two coin flips being heads = 0.5 × 0.5 = 0.25.