Estimate the range that likely contains the true population mean from a single sample. Enter the sample mean, the standard deviation, and the sample size, then pick a confidence level and the tool returns the lower and upper bounds along with the margin of error. The interval uses the standard normal z value for your chosen level, so 95 percent maps to a z of about 1.96, and the width is that z value times the standard error, which is the standard deviation divided by the square root of the sample size. A wider interval means less precision, while a larger sample tightens the range. This is a staple of surveys, quality control, and research reporting. Everything is computed locally in your browser, so your figures never leave your device.
It is a range around your sample mean that likely contains the true population mean, at the confidence level you choose.
A 95 percent level means that if you repeated the sampling many times, about 95 percent of such intervals would contain the true mean.
It needs the sample mean, the standard deviation and the sample size, plus a level of 90, 95 or 99 percent.
Estimate the range that likely contains the true population mean from a single sample. Enter the sample mean, the standard deviation, and the sample size, then pick a confidence level and the tool returns the lower and upper bounds along with the margin of error.
Yes. Confidence Interval Calculator is completely free, with no sign-up and no usage limits.
Yes. Confidence Interval Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Confidence Interval Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.