# TRIMMEAN function

This article describes the formula syntax and usage of the TRIMMEAN function in Microsoft Excel.

## Description

Returns the mean of the interior of a data set. TRIMMEAN calculates the mean taken by excluding a percentage of data points from the top and bottom tails of a data set. You can use this function when you wish to exclude outlying data from your analysis.

## Syntax

TRIMMEAN(array, percent)

The TRIMMEAN function syntax has the following arguments:

• Array    Required. The array or range of values to trim and average.

• Percent    Required. The fractional number of data points to exclude from the calculation. For example, if percent = 0.2, 4 points are trimmed from a data set of 20 points (20 x 0.2): 2 from the top and 2 from the bottom of the set.

## Remarks

• If percent < 0 or percent > 1, TRIMMEAN returns the #NUM! error value.

• TRIMMEAN rounds the number of excluded data points down to the nearest multiple of 2. If percent = 0.1, 10 percent of 30 data points equals 3 points. For symmetry, TRIMMEAN excludes a single value from the top and bottom of the data set.

## Example

Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.

 Data 4 5 6 7 2 3 4 5 1 2 3 Formula Description Result =TRIMMEAN(A2:A12,0.2) Mean of the interior of the data set contained in A2:A12, with 20 percent excluded from calculation. 3.778 