## Summary

The Excel SUM function is used to add individual values, cell references or ranges. The function is considered one of Excel's math and trig functions.

## Syntax

=SUM (number1, [number2], ...)

## Syntax Breakdown

number1
The number1 argument is required in the SUM function. This is the first number that you would like to add. The number can be a value, such as 8, a cell reference, such as A5, or a range of cells, such as C6:C15.

number2
The number2 and any subsequent number arguments are optional. These are additional numbers that you would like to add. These arguments can accept individual values, cell references, or cell ranges. The SUM function can handle up to 255 arguments.

## Usage Notes

The SUM function returns the value when specified values, cell references, or cell ranges are added together.

Working With Large or Complex Numbers
It is possible to enter =1+2+3 or =A1+B1+C1 into Excel and get the correct answer. However, when working with large or complex numbers it is advisable to enter the numbers into different cells and then use SUM.

Consider the below example. You could enter =3.14159 + 9.56487 + 15.34895 and get the same answer. Imagine how difficult it would be to go back and identify and correct an error, should one occur. By entering each value in a single cell, it becomes very easy to go back and make changes. The SUM function will update each time you change a number. SUM Errors
The SUM function will return the #REF! error if you delete a column or row. The function does not update to account for the deleted column or row.

Likewise, it is important to understand that adding a new row or column will not cause the function to update. If you are adding rows and columns it is necessary to update the function to include the additions. Failure to do so will produce inaccurate results. 