Confidence interval calculator
Calculate two-sided t, z or Wilson confidence intervals from summary statistics.
Two-sided intervals, confidence 50–99.99%, up to ten million observations. Student t intervals require at least two observations and sample SD. The z method requires known population SD. Wilson intervals model independent binary outcomes and return proportions from 0 to 1. Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.
Your result
How to use Confidence interval calculator
- Enter the observations or summary values.
- Choose the method and check its assumptions.
- Review the result and download the calculation.
Useful next steps
Choose the model before reading the result
Calculate two-sided t, z or Wilson confidence intervals from summary statistics.
Check the assumptions
Two-sided intervals, confidence 50–99.99%, up to ten million observations. Student t intervals require at least two observations and sample SD. The z method requires known population SD. Wilson intervals model independent binary outcomes and return proportions from 0 to 1.
Keep the calculation
Download the JSON for unrounded results and settings, CSV for the table, and the separate assumptions note. The calculation runs in your browser.