Returns the Weibull distribution. Use this distribution in reliability analysis, such as calculating a device's mean time to failure.
Important This function has been replaced with one or more new functions that may provide improved accuracy and whose names better reflect their usage. Although this function is still available for backward compatibility, you should consider using the new functions from now on, because this function may not be available in future versions of Excel.
For more information about the new function, see WEIBULL.DIST function.
Syntax
WEIBULL(x,alpha,beta,cumulative)
The WEIBULL function syntax has the following arguments (argument: A value that provides information to an action, an event, a method, a property, a function, or a procedure.):
 X Required. The value at which to evaluate the function.
 Alpha Required. A parameter to the distribution.
 Beta Required. A parameter to the distribution.
 Cumulative Required. Determines the form of the function.
Remarks
 If x, alpha, or beta is nonnumeric, WEIBULL returns the #VALUE! error value.
 If x < 0, WEIBULL returns the #NUM! error value.
 If alpha ≤ 0 or if beta ≤ 0, WEIBULL returns the #NUM! error value.
 The equation for the Weibull cumulative distribution function is:
 The equation for the Weibull probability density function is:
 When alpha = 1, WEIBULL returns the exponential distribution with:
Example
The example may be easier to understand if you copy it to a blank worksheet.
How do I copy an example?
 Select the example in this article. If you are copying the example in Excel Online, copy and paste one cell at a time.
Important: Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 Create a blank workbook or worksheet.
 In the worksheet, select cell A1, and press CTRL+V. If you are working in Excel Online, repeat copying and pasting for each cell in the example.
Important: For the example to work properly, you must paste it into cell A1 of the worksheet.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
After you copy the example to a blank worksheet, you can adapt it to suit your needs.

A 
B 
Data 
Description 
105 
Value at which to evaluate the function 
20 
Alpha parameter to the distribution 
100 
Beta parameter to the distribution 
Formula 
Description (Result) 
=WEIBULL(A2,A3,A4,TRUE) 
Weibull cumulative distribution function for the terms above (0.929581) 
=WEIBULL(A2,A3,A4,FALSE) 
Weibull probability density function for the terms above (0.035589) 
