Everyday utility

Confidence Interval Calculator

Calculate the confidence interval for a population mean given sample mean, standard deviation, sample size, and confidence level. Use this Data and utilities tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
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Calculator
Result
Explanation
Common questions
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How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

CI = x̄ ± Z × (σ/√n). For 95% CI, Z = 1.96. The interval means we are 95% confident the true population mean falls within this range if sampling were repeated many times.

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

Does a 95% CI mean there is a 95% chance the mean is in the interval?

No. The true mean is either in the interval or not. 95% CI means that if you repeated the experiment 100 times, about 95 of the computed intervals would contain the true mean.