Sumyard

Probability calculator

Work with independent events, combinations and binomial outcomes.

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Your inputs

Updates as you type
Enter a decimal from 0 to 1; 0.5 means 50%.
Enter a decimal from 0 to 1; 0.5 means 50%.

both independent events

12.5%

Either or both
62.5%
Neither
37.5%

Only valid under the stated independence assumption.

Calculations happen in your browser. Saving is optional.

How to use this tool

Choose independent events, combinations/permutations or an exact binomial-success count.

Enter probabilities as values from 0 to 1. The event mode assumes independence; binomial mode also assumes equal success chance on each independent trial.

Independent intersection P(A∩B)=P(A)P(B); binomial P(X=k)=C(n,k)p^k(1−p)^(n−k)

Worked example

12.5% · both independent events

Fixed example using the settings below. Monetary examples use USD; dates and times use their stated reference values. This example stays unchanged when you edit your calculation.

Example inputs
  • Calculation: Two independent events
  • Probability of A: 0.5
  • Probability of B: 0.25

Method illustration: For independent .5 and .25 events, both occur with probability .125.

Assumptions and limits

  • Event mode assumes independence. Binomial trials have the same success probability and are independent. Combinations ignore order; permutations count order.

Check or report a result

Check the units, selected calculation and assumptions first. Compare the fixed example above with your inputs to identify what changed.

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