# EXPON.DIST function

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

Returns the exponential distribution. Use EXPON.DIST to model the time between events, such as how long an automated bank teller takes to deliver cash. For example, you can use EXPON.DIST to determine the probability that the process takes at most 1 minute.

## Syntax

EXPON.DIST(x,lambda,cumulative)

The EXPON.DIST function syntax has the following arguments:

• X     Required. The value of the function.

• Lambda     Required. The parameter value.

• Cumulative     Required. A logical value that indicates which form of the exponential function to provide. If cumulative is TRUE, EXPON.DIST returns the cumulative distribution function; if FALSE, it returns the probability density function.

## Remarks

• If x or lambda is nonnumeric, EXPON.DIST returns the #VALUE! error value.

• If x < 0, EXPON.DIST returns the #NUM! error value.

• If lambda ≤ 0, EXPON.DIST returns the #NUM! error value.

• The equation for the probability density function is: • The equation for the cumulative distribution function is: ## 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 Description 0.2 Value of the function 10 Parameter value Formula Description Result =EXPON.DIST(A2,A3,TRUE) Cumulative exponential distribution function 0.86466472 =EXPON.DIST(0.2,10,FALSE) Probability exponential distribution function 1.35335283

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