Confidence interval for proportion calculator
Choose a method and calculate bounds for x successes in a sample of size n.
How do I use this page?
- Enter x and n.
- Choose a confidence level and method.
- Read the bounds and width.
What this page does not do: All methods assume independent observations with the same success probability.
Further reading
Theory — what is a confidence interval for a proportion?
A confidence interval for a proportion is a range of values expected to contain the true population proportion, estimated from x successes in a sample of size n. The calculator computes bounds using three methods: Wilson, Clopper-Pearson and Wald. The Wilson method usually gives good coverage and stays within 0–1, Clopper-Pearson inverts the exact binomial test and tends to be wider, while Wald is simple but can perform poorly for small n or proportions near the boundaries. The method you choose changes the interval width.
Frequently asked questions
Which method should I choose?
Why can Wald leave the 0–1 range?
See also
A/B test calculator
Compare two proportions in an A/B test. Calculate conversion rates, difference, uplift, z score, p value and c
A/B test planning — sample size, MDE and duration
Plan a two-proportion experiment, estimate detectable effect and traffic duration.
ACF and PACF autocorrelation calculator
Calculate ACF and PACF across time-series lags. Review the chart, reference bounds and coefficient table.