Three measures of center, plus range and spread, from one pasted list.
Computed in your browser from the list above.
For the default list (12, 7, 7, 9, 14, 21, 7), the mean is 11, the median is 9, and the mode is 7, since it appears three times and nothing else repeats. The three numbers disagree here because 21 pulls the mean upward while median and mode ignore its size entirely.
Range, minimum, and maximum come along for free below the main three, and both flavors of standard deviation are computed the same way the standard deviation calculator does, in case you need the spread as well as the center.
A quick habit worth building: look at all three together before trusting any one of them. If mean and median sit close, your data is roughly symmetric and either one is a fair summary. A wide gap between them is the tell that something, usually a handful of extreme values, is pulling the mean away from where most of the data actually sits. Mode adds a third check that neither of the other two can offer: it tells you the single most common value outright, which matters for categorical counts (most common shoe size, most common survey answer) in a way that averaging never could.
Mean adds every value and divides by the count; median sorts the values and picks the middle one. A single very large or very small value drags the mean toward it but barely moves the median, which is why home prices or salaries are usually reported as a median.
This tool reports every value tied for the highest frequency, not just the first one it finds. If two numbers each appear three times and nothing appears more often, both are listed as modes, separated by a comma, sorted from smallest to largest.
Then there is no mode, and the result field says so directly rather than guessing. A mode only exists when at least one value repeats more often than the rest.
Because a measure of center alone doesn't tell you how tightly the data clusters around it. Adding sample and population standard deviation gives a fuller picture in one pass without needing a second tool for a quick check.