Estimate how much a sample mean is likely to wander from the true population mean. Paste a list of numbers and the tool computes the sample standard deviation, then divides it by the square root of the sample size to give the standard error of the mean. The standard error shrinks as your sample grows, which is why bigger samples give more stable averages. It is the quantity that drives confidence intervals and z tests, since the margin of error is a multiple of the standard error. Do not confuse it with the standard deviation, which measures spread among individual data points rather than the precision of their average. This tool also reports the mean, standard deviation, and count so you can check the inputs. All math runs locally in your browser, so your data never leaves your device.
It estimates how much a sample mean would vary from sample to sample, showing how precisely the mean is measured.
It divides the standard deviation by the square root of the sample size.
Yes. Paste a data set and the tool finds the standard deviation and size for you, or enter them directly.
Estimate how much a sample mean is likely to wander from the true population mean. Paste a list of numbers and the tool computes the sample standard deviation, then divides it by the square root of the sample size to give the standard error of the mean.
Yes. Standard Error of the Mean Calculator is completely free, with no sign-up and no usage limits.
Yes. Standard Error of the Mean Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Standard Error of the Mean Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.