Confidence Interval Calculator

Mean confidence interval using z × σ / √n.

Confidence Interval Calculator helps you mean confidence interval using z × σ / √n. Enter sample mean, standard deviation, sample size, and z value (confidence level), review the breakdown, and use the guidance below to understand what the number means — and what it does not. What the Confidence Interval calculator does Confidence Interval Calculator is built for arithmetic, algebra, geometry, and number tools. Mean confidence interval using z × σ / √n. You enter sample mean, standard deviation, sample size, and z value (confidence level), then Simple Calculators computes the result instantly. Results use standard school and engineering formulas that run privately in your browser. How the math works Enter the Sample mean, the Standard deviation, the Sample size (a whole number of people or items) and the Z value for your confidence level (1.96 for 95%). The calculator first finds the standard error = standard deviation ÷ √(sample size), then the margin of error = z × standard error. The interval runs from mean − margin to mean + margin. It uses the normal (z) method, which assumes the standard deviation is known or the sample is reasonably large (about 30 or more). The formula: x̄ …