How to Use the Probability Calculator

Select the type of probability calculation you need, enter your values, and click Calculate. The calculator provides results in multiple formats: decimal, percentage, fraction, and odds.

Types of Probability Calculations

Single Event Probability

The most basic probability calculation: P(Event) = Favorable Outcomes / Total Outcomes. For example, rolling a 6 on a die: P(6) = 1/6 or approximately 16.67%.

Multiple Events

Calculate combined probabilities using AND, OR, and NOT operations:

P(A AND B): For independent events: P(A) × P(B). For dependent events: P(A) × P(B|A)
P(A OR B): P(A) + P(B) - P(A AND B) for any events, or P(A) + P(B) for mutually exclusive events
P(NOT A): 1 - P(A), the complement rule

Conditional Probability

The probability of event A given that event B has occurred: P(A|B) = P(A ∩ B) / P(B). This is used when events are related or dependent on each other.

Bayes' Theorem

Calculates the posterior probability based on prior knowledge and new evidence: P(A|B) = [P(B|A) × P(A)] / P(B). Essential for medical testing, spam filtering, and machine learning applications.

Understanding the Results

Decimal: Probability as a number between 0 and 1
Percentage: Probability as a percentage (0% to 100%)
Fraction: Probability as a simplified fraction
Odds: Ratio of success to failure (or vice versa)

Common Applications

Game theory and gambling calculations
Risk assessment and insurance
Medical test accuracy (sensitivity, specificity)
Quality control in manufacturing
Statistical research and data science