Hexadecimal (base 16), decimal (base 10), octal (base 8), and binary (base 2) are the most commonly used numeral systems in engineering and computing. Therefore, Excel has provided functions to convert numeric values to and from each of these systems.
The Excel Hex2Dec function converts a hexadecimal (a base16 number) into a decimal number.
The format of the function is :
Where the number argument is the hexadecimal number that is to be converted to decimal.
Note that the supplied number argument must not be more than 10 characters (40 bits) long. The most significant bit of this value denotes the sign of the number and the remaining 39 bits denote the magnitude. Negative numbers are represented using two's complement notation.
It should also be noted that, as hexadecimals use the numbers 09 and the characters af, they should be enclosed in quotation marks when they are supplied to an Excel function. (eg. The hexadecimal 11a should be input as "11a").
+ Display Hexadecimal Summary:
The following spreadsheet shows examples of the Excel Hex2Dec function. The format of the function is shown in the spreadsheet on the left and the result is shown in the spreadsheet on the right.
Formulas:

Results:

Note that, in the above example spreadsheet, the negative hexidecimal in cell A4 uses two's complement notation.
Further information and examples of the Excel Hex2Dec function can be found on the Microsoft Office website.
If you get an error from your Excel Hex2Dec function this is likely to be one of the following :
#NUM!    Occurs if the supplied number argument is not recognised as a hexadecimal number, or contains more than 10 characters 
#NAME?   
Occurs when Analysis ToolPak addin is not enabled in your Excel. + Show How to Do This in Excel 2003: 