This article describes the formula syntax and usage of the DECIMAL function in Microsoft Excel.
Description
Converts a text representation of a number in a given base into a decimal number.
Syntax
DECIMAL(text, radix)
The DECIMAL function syntax has the following arguments.

Text Required.

Radix Required. Radix must be an integer.
Remarks

The string length of Text must be less than or equal to 255 characters.

The Text argument can be any combination of alphanumeric characters that are valid for the radix, and is not case sensitive.

Excel supports a Text argument greater than or equal to 0 and less than 2^53. A text argument that resolves to a number greater than 2^53 may result in a loss of precision.

Radix must be greater than or equal to 2 (binary, or base 2) and less than or equal to 36 (base 36).
A radix greater than 10 use the numeric values 09 and the letters AZ as needed. For example, base 16 (hexadecimal) uses 09 and AF, and base 36 uses 09 and AZ. 
If either argument is outside its constraints, DECIMAL may return the #NUM! or #VALUE! error value.
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.
Formula  Description  Result  How it works 

'=DECIMAL("FF",16) 
Converts the hexadecimal (base 16) value FF to its equivalent decimal (base 10) value (255). 
=DECIMAL("FF",16) 
"F" is in position 15 in the base 16 number system. Because all number systems start with 0, the 16th character in hexadecimal will be in the 15th position. The formula below shows how it is converted to decimal: 
The HEX2DEC function in cell C3 verifies this result. 
=HEX2DEC("ff") 
Formula 

=(15*(16^1))+(15*(16^0)) 

'=DECIMAL(111,2) 
Converts the binary (base 2) value 111 to its equivalent decimal (base 10) value (7). 
=DECIMAL(111,2) 
"1" is in position 1 in the base 2 number system. The formula below shows how it is converted to decimal: 
The BIN2DEC function in cell C6 verifies this result. 
=BIN2DEC(111) 
Formula 

=(1*(2^2))+(1*(2^1))+(1*(2^0)) 

'=DECIMAL("zap",36) 
Converts the value "zap" in base 36 to its equivalent decimal value (45745). 
=DECIMAL("zap",36) 
"z" is in position 35, "a" is in position 10, and "p" is in position 25. The formula below shows how it is converted to decimal. 
Formula 

=(35*(36^2))+(10*(36^1))+(25*(36^0)) 