SUMIF

Description: Adds the cells specified by the criteria.

Syntax: SUMIF(Range, Criteria, [Sum_range])

Range is the range of cells you want evaluated.
Criteria is the criteria in the form of a number, expression, or text that defines which cells will be added. For example, Criteria can be expressed as 32, "32", ">32", "apples".
Sum_range are the actual cells to sum.

Remarks:

The cells in Sum_range are summed only if their corresponding cells in Range match the criteria.
If Sum_range is omitted, the cells in Range are summed.
You can use the wildcard characters, question mark (?) and asterisk (*), in criteria. A question mark matches any single character; an asterisk matches any sequence of characters. If you want to find an actual question mark or asterisk, type a tilde (~) before the character.
The software provides additional functions that can be used to analyze your data based on a condition. For example, to count the number of occurrences of a string of text or a number within a range of cells, use the COUNTIF function. To have a formula return one of two values based on a condition, such as a sales bonus based on a specified sales amount, use the IF function.

Example:

Suppose A1:A4 contain the following property values for four homes: $100,000, $200,000, $300,000, $400,000, respectively. B1:B4 contain the following sales commissions on each of the corresponding property values: $7,000, $14,000, $21,000, $28,000.

SUMIF(A1:A4, ">160000", B1:B4) = $63,000 [sum of the commissions for property values over 160000]