Math Calculators
Confidence Interval Calculator
Find a confidence interval for a mean.
FreeNo sign-upWorks in your browser
Enter details
Result
90% confidence interval
96.51 to 103.49
Margin of error
± 3.49
About the Confidence Interval Calculator
A confidence interval gives a range that likely contains the true population mean. Enter the sample mean, standard deviation, sample size, and confidence level, and the calculator returns the interval and the margin of error. It's a fundamental tool for reporting survey and experimental results with a stated level of certainty.
How to use the Confidence Interval Calculator
- 1Enter your sample mean, standard deviation, sample size, and confidence level.
- 2Read the result instantly — it recalculates as you type.
- 3Adjust the numbers to model different scenarios.
Frequently asked questions
What is a confidence interval?
A range around a sample estimate that likely contains the true value. A 95% CI means 95% of such intervals would capture the true mean.
How does sample size affect it?
Larger samples shrink the margin of error, giving a tighter, more precise interval.