Mean Calculator
One Number to Summarize an Entire Data Set
The arithmetic mean is the single most common way to compress a list of numbers into one representative value. It underlies grade point averages, quarterly sales reports, batting averages, and the "average" temperature quoted on the evening news. It's simple to compute, but it hides a weakness worth knowing before you lean on it: every value in the set pulls the mean toward itself, including the extreme ones.
The Formula
Add every number in the data set, then divide by how many numbers there are. That's the entire calculation — the complexity in statistics usually comes from what you do with the mean afterward, not from computing it.
Where a Straight Average Falls Short
Because the mean factors in every data point equally, a single unusually large or small value can drag it away from where "most" of the data actually sits. Compare these five annual salaries, in thousands of dollars:
| Salaries ($000s) | Mean | Median |
|---|---|---|
| 40, 42, 45, 48, 300 | 95.0 | 45 |
One senior salary of $300k pulls the mean above every other value in the set except itself, while the median stays anchored to where the typical employee actually falls. When you suspect outliers are present, run both this calculator and the Median Calculator side by side.
Common Uses
- Academic grading — averaging test scores or assignment grades into a final mark.
- Business reporting — average order value, average response time, average daily revenue.
- Scientific measurement — taking repeated readings of the same quantity and averaging out random measurement error.
- Sports statistics — batting averages, points per game, and similar per-event summaries.
How to Use This Calculator
- Enter your numbers into the values field, separated by commas (for example,
4, 8, 15, 16, 23, 42). - Select Calculate.
- The result shows the mean along with the sum and count used to compute it.
Related Calculations
If your data set has extreme values, cross-check it against the Median Calculator, which isn't affected by outliers. To see how spread out your values are around this mean, use the Standard Deviation Calculator.