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Probability Calculator
Calculate the probability of an event using favorable outcomes and total possible outcomes.
Calculate Probability
Enter the number of favorable outcomes and total possible outcomes.
FORMULA
Probability Formula
When all possible outcomes are equally likely, probability can be calculated by dividing the number of favorable outcomes by the total number of possible outcomes.
Probability = Favorable Outcomes ÷ Total Possible Outcomes
To express the probability as a percentage, multiply the probability by 100.
EXAMPLE
Probability Example
A standard six-sided die has six possible outcomes. If you want to know the probability of rolling a 2, there is one favorable outcome.
Therefore:
Probability = 1 ÷ 6
This equals approximately 16.67% .
PROBABILITY SCALE
Understanding Probability
Probability ranges from 0 to 1 when expressed as a decimal, or from 0% to 100% when expressed as a percentage.
A probability of 0 means an event is impossible.
A probability of 1 means an event is certain.
A probability between 0 and 1 represents an event that may or may not occur.
ODDS
Probability and Odds
Probability and odds describe uncertainty in different ways.
If there are 2 favorable outcomes out of 10 possible outcomes, the probability is 2/10, or 20%.
The odds in favor are 2 to 8, which can be simplified to 1 to 4.
TYPES
Common Types of Probability
Simple Probability: Measures the chance of a single event occurring.
Compound Probability: Deals with two or more events.
Conditional Probability: Measures the probability of an event given that another event has already occurred.
Experimental Probability: Based on observations from an experiment or trial.
REAL-WORLD USES
Where Probability Is Used
Probability is used in mathematics, statistics, science, finance, insurance, games, weather forecasting and risk analysis.
It can help estimate the likelihood of events when the possible outcomes and their probabilities are known.
IMPORTANT
Probability Calculator Notes
The basic calculation used by this calculator assumes that the possible outcomes are equally likely.
The number of favorable outcomes cannot be greater than the total number of possible outcomes.
A probability cannot be less than 0 or greater than 1.
FAQ
Frequently Asked Questions
What is probability?
Probability is a numerical measure of how likely an event is to occur.
What is the basic probability formula?
Probability is calculated by dividing favorable outcomes by total possible outcomes when the outcomes are equally likely.
Can probability be greater than 100%?
No. A valid probability ranges from 0% to 100%.
What does a probability of 50% mean?
It means the event has a one-half probability under the stated probability model.
What does probability of zero mean?
A probability of zero means the event is considered impossible under the model.
What does probability of one mean?
A probability of one, or 100%, means the event is certain under the model.
Is this Probability Calculator free?
Yes. Fashnza's Probability Calculator is free to use.
Does this calculator store my numbers?
No account is required. Calculations are performed directly in your browser.
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