Understanding Probability
Probability is the mathematical branch that quantifies how likely an event is to occur. It ranges from 0 (impossible) to 1 (certain), or 0% to 100%. Whether you are calculating card odds in poker, weather forecasts, or risk assessments in business, probability forms the bedrock of decision-making under uncertainty.
Our Probability Calculator automates single-event and compound probability equations instantly. If you need to evaluate permutations or combinations to find your total possible outcomes first, you can use our Factorial Calculator.
Core Rules of Probability
1. Single Event Rule
The chance of a single event $A$ happening is the ratio of favorable outcomes to total possible outcomes.
Formula: P(A) = Favorable / Total
2. The Complement Rule
The probability that an event will not happen is simply 1 minus the probability that it will happen.
Formula: P(not A) = 1 - P(A)
Frequently Asked Questions (FAQs)
What is probability?
Probability is the measure of the likelihood that an event will occur. It is expressed as a number between 0 and 1 (or 0% to 100%), where 0 means the event is impossible and 1 means it is certain.
How do you calculate the probability of a single event?
The probability of a single event is calculated by dividing the number of favorable outcomes by the total number of possible outcomes: P(A) = (Favorable Outcomes) / (Total Outcomes).
What is the difference between 'A and B' vs 'A or B'?
'A and B' calculates the probability that both independent events occur together (multiplication of probabilities). 'A or B' calculates the probability that either event A occurs, event B occurs, or both occur.