Binomial probability
Calculate binomial probability and see the working behind your result.
Inputs
Use the units shown—
Enter your values and select Calculate.
Formula & explanation
P(X=r) = nCr pʳ(1−p)ⁿ⁻ʳ
Variables & units
- Number of trials
- Numeric value · minimum 0, maximum 50
- Number of successes
- Numeric value · minimum 0, maximum 50
- Success probability per trial
- Numeric value · minimum 0, maximum 1
Worked example
Exactly 2 successes in 5 fair trials has probability 0.3125.
Assumptions
This is the probability of exactly r successes, not at least r.
Formula version 1.0.0. JavaScript floating-point arithmetic applies. Results display up to 6 decimal places; stored values retain available precision. Use the units shown.
Practice with an example
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