Probability Calculator
Calculate event probability, its complement and odds from equally likely outcome counts.
What would you like to do next?
Translate outcome counts into probability and odds
Enter the number of favorable outcomes and the total number of outcomes in a sample space where each outcome is equally likely. The calculator divides the counts for event probability, subtracts from one for the complement and expresses odds in favor when unfavorable outcomes remain. Showing all three formats helps connect fractions, percentages and odds without changing the underlying event.
Validate the equally likely assumption first
Counting outcomes works only when the listed possibilities have equal probability and the sample space is complete. Weighted events, dependent trials, replacement rules and empirical data need a different model. Define the event precisely, avoid double-counting outcomes and use an appropriate statistical method when likelihoods are not uniform.
Frequently asked questions
How is simple probability calculated?
Favorable outcomes are divided by total equally likely outcomes.
What is the complement?
It is the probability that the entered event does not occur.
Can I use weighted outcomes?
Not with this count-only model; unequal likelihoods require weights or another method.