Fractional Arithmetic In Excel

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This page describes how do perform Fractional Arithmetic in Excel.   For example, you can use fractional arithmetic to work with feet and inches, allowing you to enter values as feet.inches without having to convert inches to decimal portions of feet.  The Analysis ToolPak add-in module, which comes with Excel, provides two functions for doing this:  DOLLARDE and DOLLARFR.    As you might guess from their names, these functions are intended to be used with financial data, such as stock prices, that are typically expressed in eighths or sixteenths, rather than in decimal values.  However, you can use the functions to work with any data you need to. 

The DOLLARDE and DOLLARFR functions are part of the Analysis Tool Pack add-in module.  Click here for more information about using the ATP.  

When working with numbers in a fractional form, you will need to convert from the fractional form into standard decimal form, and then convert the decimal form back to fractional form.  The  DOLLARDE  function (dollar-decimal) takes a fractional number, such as feet.inches, and converts it to a standard decimal value.  The DOLLARFR function (dollar-fraction) takes a decimal value and converts it back to the fractional form. 

We'll use feet and inches as an example.  Suppose you're working with measurements in feet and inches.  You can enter these values into worksheet cells as  feet.inches.  For example, 10.06 will represent 10 feet, 6 inches, and 10.1 will represent 10 feet, 10 inches.  Note that for values less than 10 inches, you must include the leading zero in the fractional portion of the number, for example 10.06.  If you enter 10.6, the DOLLARDE function will interpret this as 10 feet and 60 inches, or 15 feet. 

Before you can do anything with the value, you must convert it to a real, decimal number.  This is where the DOLLARDE function comes in.  The syntax for DOLLARDE is:

=DOLLARDE(value,fraction)

where value is the value to convert to decimal, and fraction is the fractional base.  For feet and inches, the fraction would be 12.  So if our value of 10.06, or 10 feet and 6 inches, is in cell A1, we'd use the function

=DOLLARDE(A1,12)

This will return the value 10.5.   Now, you can use this value whenever you need to use it in arithmetic, for example in determining an area. 

The DOLLARFR function works in the opposite direction of  DOLLARDE. In other words, it converts decimal values back to fractional representations.  For example, it will convert 10.5 back to 10.06.   The syntax for DOLLARFR is:

=DOLLARFR(value,fraction)

where value is the value to convert to decimal, and fraction is the fractional base.  For feet and inches, the fraction would be 12.  So if our value of 10.5 is in cell A1, we'd use the function

=DOLLARFR(A1,12)

This will return the value 10.06.  

Unfortunately, neither the DOLLARDE nor the DOLLARFR function accepts arrays.  Therefore, you can't use them in array formulas.