Converting to Octal

There are four types of numbering systems commonly used in programming: binary, octal, decimal, and hexadecimal. Each is simply a different method of expressing the exact same values. Excel makes it easy to convert between decimal and octal numbers, and provides two worksheet functions for that very purpose.

The first function is the DEC2OCT function. Suppose you have a decimal value in cell B7, and you want to know how to express that value in octal. In a different cell you could use the following formula:


If the value in B7 was 456, the result of the above formula would be 710. An interesting fact (and potential “gottcha”) is that when the conversion is completed, Excel considers the result to be a number. Thus, if you added 8 to the resulting value above (710), Excel would return 718-a value impossible in octal. This simply means that Excel doesn’t keep track of the numbering system used in a particular cell; it expects you to do that.

If you want to convert numbers back the other way, from octal to decimal, you can use the OCT2DEC worksheet function:


If you try to use this function with a value that is clearly not octal (such as 718), then Excel returns a #NUM! error value.