Let Excel be your calculator. With a simple formula Excel can sum numbers automatically.

Select an empty cell and type an equal (=) sign.

Type your first number followed by a plus (+) sign between each number that you want to sum.

Press Enter to get the formula result.
For example:

=54+89 (result: 143)
You can also create the same formula by using cell references (such as A1 and B1) instead of using numbers.
For example:

=A1+B1 (result: 143)
Or you can combine cell references and numbers.

=A1+B1+20 (result: 163)
You can either type the cell reference or click the cell you want to include in the formula. For example, to create a formula that adds A1, B1, and 20, you can type the equal (=) sign, click A1, type a plus (+) sign, click B1, type a plus (+) sign, type 20, and then press Enter to get the result of 163.
Excel highlights the cells used in the formula.
Tip: When you have columns or rows to sum, there’s an automated way Excel can sum numbers for you, by clicking AutoSum.