Confidence Interval Calculator

Calculate a confidence interval for a mean (Z-interval).

Mean (x̄)

Standard Deviation (σ)

Sample Size (n)

Confidence Level (%)

Tip: choose 90%, 95% or 99% to use common Z values.

Result—

Example: mean 50, σ 10, n 100, 95% → 48.04 to 51.96

Formula

CI = x̄ ± z × (σ ÷ √n)