How this is calculated
Mean = sum of all values ÷ count. Median = the middle value after sorting, or the average of the two middle values when the count is even. Mode = the most frequently occurring value, and a dataset can have more than one, or none if every value appears exactly once.
Worked example on 2, 4, 4, 4, 5, 5, 7, 9: the sum is 40 and the count is 8, so the mean is 5. Sorted, the two middle values are 4 and 5, so the median is 4.5. The value 4 appears three times, more than any other, so the mode is 4.
Here the three measures land close together because the data is fairly symmetric. Add a single value of 200 and the mean jumps to 26.2 while the median moves only to 5 — a clean demonstration of which measures resist outliers.
When each average is the right one
Use the mean for symmetric data where every value should carry equal weight — test scores, measurement repeats, daily temperatures. It uses all the information in the dataset, which is its strength and its vulnerability.
Use the median for skewed data or anything with outliers. Income, house prices, wealth, page load times and wait times are all reported as medians by people who know what they are doing, because a small number of extreme values makes the mean unrepresentative of any actual case.
Use the mode for categorical data, where the mean is meaningless — the most common shoe size, the most frequent response, the most popular option. It is also the only one of the three that must be a value actually present in the data.
Why the gap between mean and median matters
The direction of the gap tells you the direction of the skew. Mean above median means a long right tail — a few large values. Mean below median means a long left tail. Roughly equal means the distribution is close to symmetric.
This is why 'average income' is such a contested phrase. Mean income in most countries sits well above median income, because high earners pull the mean up while the median tracks what a typical person actually receives. Both numbers are correct; they answer different questions, and quoting one while implying the other is among the most common ways statistics mislead without technically lying.
How to use the mean, median, mode calculator
- Paste your numbers. Commas, spaces or new lines all work, so a spreadsheet column pastes straight in.
- Compare mean against median. If they differ noticeably, your data is skewed and the median is probably the more representative figure.
- Check the mode for repeated values. Most useful when values repeat meaningfully. On continuous measurements with no repeats there is no mode, which is a valid result rather than an error.