You can create a simple formula to add, subtract, multiply, or divide values in your worksheet. Simple formulas always start with an equal sign (=), followed by constants that are numeric values and calculation operators such as plus (+), minus (), asterisk(*), or forward slash (/) signs.
For example, when you enter the formula =5+2*3, the last two numbers are multiplied and added to the first number to get the result. Following the standard order of mathematical operations, multiplication is performed before addition.

On the worksheet, click the cell where you want to enter the formula.

Type the = (equal sign) followed by the constants and operators you want to use in the calculation.
You can enter as many constants and operators in a formula as you need, up to 8192 characters.
Tip: Instead of typing the constants into your formula, you can select the cells (like B12:B15) that contain the values you want to use and enter the operators in between selecting cells.

Press Enter.
Note:

To quickly add values, you can use AutoSum instead of entering the formula manually (Home tab, Editing group).

You can also use a function (like the SUM function) to calculate values in your worksheet.

To take it one step further, you can use cell references in a formula instead of the actual values in a simple formula.
Examples
The workbook below shows examples simple formulas. You can change any of the existing formulas, or enter your own formulas to learn how they work and see their results.
Data 

2 

5 

Formula 
Description 
Result 
'=A2+A3 
Adds the values in cells A1 and A2 
=A2+A3 
'=A2A3 
Subtracts the value in cell A2 from the value in A1 
=A2A3 
'=A2/A3 
Divides the value in cell A1 by the value in A2 
=A2/A3 
'=A2*A3 
Multiplies the value in cell A1 times the value in A2 
=A2*A3 
'=A2^A3 
Raises the value in cell A1 to the exponential value specified in A2 
=A2^A3 
Formula 
Description 
Result 
'=5+2 
Adds 5 and 2 
=5+2 
'=52 
Subtracts 2 from 5 
=52 
'=5/2 
Divides 5 by 2 
=5/2 
'=5*2 
Multiplies 5 times 2 
=5*2 
'=5^2 
Raises 5 to the 2nd power 
=5^2 