What the calculator does
The arithmetic mean is the sum of the values divided by their count. The median is the central value after sorting. If there are an even number of values, the median is the mean of the two central values. Repeated values count each time they appear; the tool does not remove duplicates.
For 12, 14, 15, 16, and 18, the total is 75 and the count is five, so the mean is 75 ÷ 5 = 15. The sorted list’s third value is also 15, so both summaries agree. That agreement is a feature of this example, not a rule for all datasets.
What to ask before choosing an average
Decide what a value represents. A list of household bills, for example, should not accidentally mix monthly and yearly costs. The calculator treats every value as equally weighted and has no way to know its unit or meaning. It does not compute a weighted mean or interpret missing observations.
The mean can be useful when totals matter: multiplying the mean by the count reconstructs the total before rounding. The median describes the central position and is less sensitive to one extremely large or small value. Neither number explains the full distribution, so look at the minimum, maximum, and sorted values too.
Try an even-sized example
Enter 2, 4, 8, 100. The central pair is 4 and 8; their mean gives a median of 6. The arithmetic mean of all four numbers is 114 ÷ 4 = 28.5. The median does not have to be a value that appears in the list. Now remove 100 and compare both results again.
Input and precision limits
The tool accepts signed decimal numbers and scientific notation such as 1e3. A comma is always a separator: enter 1000 for one thousand, not 1,000, which means two values here. Blank input, unrecognized tokens, excessive values, and numbers beyond the documented limit return an error rather than being silently ignored.
Calculations use JavaScript floating-point arithmetic and results are rounded to six decimal places for display. Very small values can display as zero. This is an educational tool, not an exact-decimal financial calculation system or a statistical inference package. It does not produce confidence intervals or prove that a dataset represents a population.
Check the underlying concepts
See the NIST explanation of location measures and our mean vs. median guide for more context. If the tool produces an unexpected result, report the inputs and expected calculation using a non-sensitive example.