Probability Calculator
Calculate single event probabilities, odds, and independent multi-event unions and intersections.
Basic Probability
Probability
0.5
Percentage
50.00%
Odds (for:against)
3:3
Combined Events (A and B independent)
P(A or B)
0.65
P(A and B)
0.15
P(not A)
0.5
P(not B)
0.7
How to Use the Probability Calculator
- For basic probability, enter the number of favorable outcomes and total possible outcomes.
- For combined events, enter probabilities P(A) and P(B) between 0 and 1.
- Examine the resulting percentages, odds ratios, and Boolean event logic.
Formulas & Principles
Basic Probability: P(E) = Favorable Outcomes / Total Outcomes
Complement Rule: P(not A) = 1 - P(A)
Union (Independent): P(A or B) = P(A) + P(B) - P(A) × P(B)
Intersection (Independent): P(A and B) = P(A) × P(B)
Frequently Asked Questions
How is basic probability defined?
Probability is the ratio of favorable outcomes divided by the total number of equally likely possible outcomes (P = Favorable / Total).
What does P(A and B) represent for independent events?
For independent events, the probability of both occurring simultaneously is the product of their individual probabilities: P(A and B) = P(A) × P(B).
What is the addition rule for probability?
The probability that event A or event B occurs is given by: P(A or B) = P(A) + P(B) - P(A and B).
Why this calculator matters
This calculator helps solve mathematical problems faster and with fewer manual arithmetic mistakes. It is useful for studying, research verification, technical engineering checks, and everyday problem-solving.
When to use it
Use it when you need a fast answer, a cross-check for manual calculations, or a clear step-by-step verification of your result.
Quick tips
Double-check your inputs, keep units consistent across all fields, and verify boundary conditions.
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