The Excel TRIMMEAN function returns the mean of a data set after discarding a percentage of the highest and lowest values — a robust average that ignores outliers.
Syntax
| Argument | Description | |
|---|---|---|
array | Required | The data set to average. |
percent | Required | The fractional number of points to trim, e.g. 0.2 for 20%. The total is split between the high and low ends. |
How to use it
TRIMMEAN removes the most extreme values from both ends before averaging, so a single huge or tiny outlier can't drag the result around — the way some judged sports drop the highest and lowest scores.
Excel multiplies percent by the count, rounds down to the nearest even number, and removes half from each end. So 20% of 10 points = 2 points = 1 trimmed from each end.
Always even, always balanced: because the trim count is rounded down to an even number, TRIMMEAN always removes the same number of values from the top and bottom — keeping the average symmetric.
Try it: interactive demo
Pick a TRIMMEAN example to see the formula and its result.
Practice workbook
Frequently asked questions
How does TRIMMEAN decide how many points to drop?
percent by the number of values, rounds that down to the nearest even integer, and removes half from the top and half from the bottom.Why round down to an even number?
How is TRIMMEAN different from MEDIAN?
What percent value should I use?
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