The SUM Function adds a group of numbers together that you specify. This function is the workhorse of Microsoft Excel worksheets and must be learned.

The SUM function is a computer program that you run from a worksheet cell formula. It adds a group of numbers together generally from a worksheet area you specify (called a range). You run the SUM worksheet function by typing its name in a formula then followed by the information it is suppose to calculate. Since adding cell values together on the worksheet is a very common task and can take a long time if you were to use a standard formula like =A1+A2+A3..., this function allows you to perform an addition calculation very rapidly on a great deal of numbers. This function is capable of adding 2 cell values together or thousands of cell values together. The SUM worksheet function is most commonly used to add a row of numbers or a column of numbers together on the worksheet.

Whenever you type a formula in a worksheet cell, this is called syntax or grammar. The general SUM function syntax has a format like this when you type it in a worksheet cell:

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

Where number1, [number2] ..... are called the function argument list. Remember, you are running a computer program at this point so the program needs information to operate and that is why there is an argument list. When you see an argument list and you see square brackets [ ] around the argument name, this means the argument is optional and you do not have to include it when typing unless you need it. So for the syntax above, you need to include one argument for the SUM function when typing it in a worksheet cell formula in order for it to calculate correctly. How many arguments can be placed in the list is dependent upon the Excel version you are using. What argument values can be used are discussed below. Remember functions expect certain things in their argument lists, if you do not put the correct information in the list they will generate an error when run.

Since the SUM function is a computer program, it runs when you press Enter to enter the formula that contains it. If any of the arguments are wrong, the function will return an error.

When typing the SUM function in a worksheet cell formula, you need to replace the number1... argument list with arguments separating each one with a comma (,). Since the SUM function adds things it expects numbers. Some typical arguments you can use are:

Argument Type | Cell Formula | Example Explanation |

Cell Reference | = SUM( A1, B1 ) | Finds the sum of the cell values from A1 and B1 |

Range Reference | = SUM( A1:A10 ) | Finds the sum of the cell values between cells A1 and A10 |

Column Reference | = SUM( C:C ) | Finds the sum of the cell values from Column C |

Row Reference | = SUM( 1:1 ) | Finds the sum of the cell values from Row 1 |

Numbers | = SUM( 100, 200, A1 ) | Finds the sum between 100, 200 and cell A1's value |

Multiple Columns/Rows | = SUM( A1:A10, C1:C10 ) | Finds the sum of the cell values from A1 to A10 and from C1 to C10 |

Cell and Range Names | = SUM( Sales_2012 ) | Finds the sum of the values in the range named Sales_2012 * |

* It is possible to name a cell or group of cells on a worksheet and use that name in place of a range reference or cell reference. Consult Excel help on how to name a cell.

The worksheet seen below contains some typical worksheet formulas that run the SUM worksheet function. Pay close attention to the argument list and the syntax used to write the formula.

A | B | C | |

1 | Quantity | = SUM( A1:A5 ) | Returns the sum value from the range A1 to A6. SUM will ignore the header and TRUE |

2 | 100 | = SUM( A1:A6 ) | The SUM function will error out because there is an error in cell A6 |

3 | 200 | ||

4 | 300 | ||

5 | TRUE | ||

6 | #DIV/0! | ||

7 |

- Numbers, TRUE, FALSE and text representations of numbers that are typed directly into the SUM function argument list are counted.
- If using a range, only numbers in that range are counted. Empty cells, TRUE, FALSE or numbers displayed as text in the range are ignored.
- References (cell or ranges) or formulas that produce error values or text that cannot be translated into numbers will cause an error.

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