Formulas are a way of calculating one cell's entry based on what is in other cells.
You enter a formula in a cell just like you enter other data, by clicking and typing. A formula cell must start with an equals sign so that Excel knows it's a formula. Cell references are used to identify cells in the formula.
Example 1: We can calculate "two times the entry in C4 minus 3 times the entry in D2" and put the result in D5 using the formula =2*C43*D2 in cell D5 as shown below:
A 
B 
C 
D 

1 

2 
2 

3 

4 
7 

5 
8 
Notice that the actual formula doesn't appear in D5, only the result. You can see or edit the formula by clicking on a cell in Excel; the formula will appear in the entry area, as shown in the screenshot below:
Excel can carry out all the usual arithmetic operations on cells, plus a lot more. The common symbols Excel uses are listed below:
Symbol 
Meaning 
+ 
plus 
 
minus 
* 
times 
/ 
divided by 
^ 
exponent 
You can also use parentheses to group expressions. (When in doubt, use more parentheses!)
Note: the exponential function is not represented using ^. Excel has a special function EXP() to represent the exponential function; see Special Functions for more information.
More Examples: