A circular reference is caused by including within a formula a reference to the cell storing the formula. It often occurs when the user selects the range for a function and inadvertently includes the formula location itself. For instance, if you stored the following formula in cell A3, the result is a circular reference:
= A1 + A2 + A3
If you try to enter a circular reference, Excel alerts you to the problem by displaying a dialog box. This dialog box requests you to click OK if the circular reference was a mistake or click Cancel if it was intentional. Unfortunately many users react without carefully reading the dialog box and press Cancel or press Esc just to get rid of the dialog box. Oops! The formula returns zero and the circular reference remains in your worksheet.
In the status bar, at the bottom of the screen, Excel displays Circular References and the address of the offending formula. Every help text I have seen indicates that the address of the circular reference is listed in the status bar. This is true only if the circular reference is on the current worksheet. The Circular References notation is displayed any time a circular reference is present in any open workbook.
If you notice the Circular References notation without an accompanying address, you can spend a lot of time working through every sheet of every open workbook until you see the address. There is a faster way to find circular references, regardless of where they are. When a circular reference is in existence, you can quickly find them by using the ribbon!
Display the Formulas tab of the ribbon, click the down-arrow next to the Error Checking tool (in the Formula Auditing group), choose Circular References, and you will see a list of the circular references that Excel has detected. Click the one you want, and the cell that contains the circular reference is displayed.