No More Custom Formats Can Be Added

Some day, as you are working with a large workbook, you may be surprised by an error message that pops up. You may be trying to change the formatting of a cell, and Excel refuses to make the change and instead displays a message that says "No more custom number formats can be added." Why does Excel do this?

Every time you change the format of a cell to a "custom format" you are adding formats to Excel. According to Excel's specifications, the number of custom formats you can use is only limited by memory, but you must remember that limitation is theoretical--it is very possible that you will run out of space for custom formats long before you run out of memory.

Unfortunately, there is no easy way to correct this problem. Once a custom format is created, Excel "remembers" it, and you cannot get rid of it easily. There are a few different things you can try, however.

• Use File | Save As to save the workbook under a different name.
• Save the worksheets as HTML files, and then load them from HTML back into Excel. (You may loose some formatting during the round trip, but it should help clear things up.)
• Copy the contents of each worksheet to a new, blank workbook. Don't use Edit | Move or Copy Sheet, as this can also move or copy your custom formats. You should instead select all the cells in a worksheet, press Ctrl+C, go to the new worksheet, and press Ctrl+V.