Returns the harmonic mean of a data set. The harmonic mean is the reciprocal of the arithmetic mean of reciprocals.
Syntax
HARMEAN(number1,number2,...)
Number1,number2, ... are 1 to 30 arguments for which you want to calculate the mean.
Remarks

The arguments must be either numbers or column references that contain numbers.

If a column reference argument contains text, logical values, or is empty, those values are ignored; however, arguments with the value zero are included.

If any data point ≤ 0, HARMEAN returns the #NUM! error value.

The harmonic mean is always less than the geometric mean, which is always less than the arithmetic mean.

The equation for the harmonic mean is:
Example
Col1 
Col2 
Col3 
Col4 
Col5 
Col6 
Col7 
Formula 
Description (Result) 
4 
5 
8 
7 
11 
4 
3 
=HARMEAN([Col1],[Col2],[Col3],[Col4],[Col5],[Col6],[Col7]) 
Harmonic mean of the data (5.028376) 