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Probability Calculators

Independent Events Calculator

Probability that an event happens at least once, every time or never over repeated independent trials.

Enter values

Results update as you type.

Result

P(at least once)

0.65132156

P(every time)
1 × 10^-10
P(never)
0.34867844
Expected occurrences
1

About the Independent Events Calculator

Probability that an event happens at least once, every time or never over repeated independent trials.

Also known as: at least once probability, repeated trials, probability of at least one, multiple independent events.

How to use this calculator

  1. Enter probability per trial, number of trials.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

P(at least one) = 1 − (1 − p)ⁿ

Worked example

Using the values pre-filled in the calculator above:

  • Probability per trial = 0.1
  • Number of trials = 10

the calculator returns:

  • P(at least once): 0.65132156
  • P(every time): 1 × 10^-10
  • P(never): 0.34867844
  • Expected occurrences: 1