Excel TRIMMEAN Function

The Excel TRIMMEAN function calculates mean (average) while excluding outliers. The number of data points to exclude is provided as a percentage.

TRIMMEAN works by first excluding values from the top and bottom of a data set, then calculating mean. The number of data points is provided as a percentage. The percentage can be input either in decimal format or percent format:

=TRIMMEAN(A1:A100,0.1) // exclude 10%
=TRIMMEAN(A1:A100,10%) // exclude 10%
=TRIMMEAN(A1:A100,0.2) // exclude 20%
=TRIMMEAN(A1:A100,20%) // exclude 20%

It's important to note that TRIMMEAN rounds excluded data points down to the nearest multiple of 2. For example, with 50 data points, 10% equals 5 values. In this case, TRIMMEAN will round 5 down to 4, then exclude two values from the top, of the data set, and two values from the bottom of the data set.