Mean, median and mode
All three averages at once, because they answer different questions — and with the mode saying plainly when there is not one, which most calculators will not do. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
A dataset can have no mode, and most calculators will not say so
If every value appears exactly once there is no most common value. The honest answer is none. Many calculators return the first value, or the smallest, or list the whole dataset back as though all of it were the mode.
And a dataset can have several. When two values tie there is no rule that picks between them, so this page gives both.
The mean is not the average, exactly
“Average” is not a defined term — the mean, the median and the mode are all averages, and they answer different questions. The mean is the balance point. The median is the middle one. The mode is the most common.
On a symmetric dataset they land close together. On a skewed one they separate, and which of them somebody quotes tells you something about what they wanted you to conclude. That is why all three are above rather than one.
Midrange, which nobody should use
The midrange is halfway between the smallest and largest value. It is here because it appears on other calculators and because knowing what it is worth is useful: it depends on exactly two of your numbers and ignores every other one, so a single mistyped value moves it as far as you like.