Formula in Excel 2007
How to count cells by criteria
Use COUNTIF if you need to sum values for a particular person or other criterion.
How to sum cells by criteria
Use SUMIF if you need to sum values for a particular person or other criterion.
Basic Formula operators
There are several operators that could be used in formulas.
How to avoid misleading numbers
Applying a number format to a cell doesn't change the value, but only how the value appears in the worksheet. Formatting can play a joke with you, e.g., sum of values seems incorrect because Excel displays a limited number of decimal places and their sum is not equal to the real sum.
Using the formula bar as a calculator
If you simply need to perform a calculation, you can use the Formula bar as a calculator.
Referencing cells outside the worksheet
Formulas can refer to cells in other worksheets-and the worksheets don't even have to be in the same workbook. Excel uses a special type of notation to handle these types of references.
Shortcut key to switch between relative, absolute and mixed references
You can enter nonrelative references (absolute or mixed) manually by inserting dollar signs in the appropriate positions, or you can use a handy shortcut - F4 key.
Creating and using named ranges
Range names is a powerful Excel feature which allows you to give a symbolic name for the cell or range of cells to be later used as convenient replacement for cell/range address in formulas.
Excel Formula auditing tools
If you would like to better understand how some of these complex array formulas work, consider using a handy tool - Formula Evaluator:
Counting the number of unique values
You can easily count the number of unique values of the range using a simple formula.