Basic Description

The Excel LOGNORM.INV function calculates the inverse of the Cumulative Log-Normal Distribution Function of x, for a supplied probability. The Lognorm.Inv function is new in Excel 2010 and so is not available in earlier versions of Excel. However, the function is simply a new version of the Loginv function that is available in earlier versions of Excel.

Syntax: LOGNORM.INV( probability, mean, standard_dev )

Where the function arguments are:

probability The value at which you want to evaluate the inverse function
mean The arithmetic mean of ln(x)
standard_dev The standard deviation of ln(x)


Lognorm.Inv Function Example

Plot of Inverse Log-Normal Cumulative Distribution Function with Mean=2 and Standard Deviation=0.2

Inverse of Log-Normal Cumulative Distribution of x with
mean ln(x) = 2 & standard deviation ln(x) = 0.2

The chart on the right shows the the Inverse Log-Normal Cumulative Distribution Function for a variable x. The mean of ln(x) = 2 and the standard deviation of ln(x) = 0.2.

If you want to calculate the value of x for a probability of 0.3, this can be done using the Excel Lognorm.Inv function, as follows:

=LOGNORM.INV( 0.3, 2, 0.2 )

This gives the result 6.653346076.


Lognorm.Inv Function Errors

If you get an error from your Excel Lognorm.Inv function this is likely to be one of the following:

#NUM! Occurs if either the supplied probability argument is ≤ 0 or ≥ 1 or the supplied standard_dev argument is ≤ 0
#VALUE! Occurs if any of the the supplied arguments are non-numeric.

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