Confidence Interval Calculator (for a Mean)
Enter the sample mean, standard deviation, sample size and confidence level to calculate the confidence interval.
Confidence Interval Calculator (for a Mean)
Calculate a confidence interval around a sample mean at a chosen confidence level.
This calculator provides an estimate for general informational purposes only. It is not a substitute for professional financial, mechanical or engineering advice.
This calculator adds and subtracts the margin of error (based on standard deviation, sample size and confidence level) from the sample mean to produce the upper and lower bounds of the confidence interval.
Example
- With the default values shown above, this calculator returns: Margin of Error ≈ 2.94; Lower Bound ≈ 47.06; Upper Bound ≈ 52.94.
Frequently Asked Questions
What is a confidence interval?
A confidence interval gives a range that's likely to contain the true population mean, with the chosen confidence level (e.g. 95%) describing how often intervals built this way would contain the true value across repeated sampling.
What is the formula?
Confidence Interval = Sample Mean ± (z-score × Standard Deviation ÷ √Sample Size).