Confidence Interval Calculator

Calculate confidence intervals for a population mean given sample statistics.

Sample Mean (x̄)

Sample Size (n)

Standard Deviation (σ)

Confidence Level

Lower Bound

Upper Bound

Margin of Error

Standard Error

How It Works

The confidence interval gives a range of values that is likely to contain the true population mean. Standard Error = σ/√n. Margin of Error = z* × SE, where z* depends on the confidence level.

CI = x̄ ± z* × (σ / √n) | z*(90%)=1.645, z*(95%)=1.96, z*(99%)=2.576

About this Calculator

The Confidence Interval Calculator is a free, easy-to-use tool for CI, margin, error. Simply enter your values and get instant, accurate results — no signup, no ads, no tracking. All calculations run locally in your browser, so your data stays completely private.

Privacy Note: All calculations are performed locally in your browser. No data is ever sent to a server or third party.