Wilson Proportion Interval Calculator
Construct a Wilson score interval for independent binary outcomes.
Your result
MATHEnter your values and select calculate.
On this page How it works & practical examples
How to use the Wilson Proportion Interval Calculator
Count successes and total trials in one independent binary sample. The primary output is the interval width in percentage points, while the two endpoints appear separately.
The calculation
Worked example
50 successes in 100 independent observations at z = 1.96 give a Wilson interval of approximately 40.383% to 59.617%.
Assumptions and limits
No finite-population, survey design or repeated-testing correction is applied. The chosen multiplier controls the nominal normal-based level; actual coverage can vary with the true proportion and sample size.
Common questions
Which inputs should I use?
Count successes and total trials in one independent binary sample. The primary output is the interval width in percentage points, while the two endpoints appear separately.
What does the result exclude?
No finite-population, survey design or repeated-testing correction is applied. The chosen multiplier controls the nominal normal-based level; actual coverage can vary with the true proportion and sample size.