In Microsoft Excel, SUMIF is a formula used to add together the values over a range of cells. The basic SUM function adds values in a range of cells, regardless of what the values are. With SUMIF, a user can define specific criteria that have to be met for the values in a range of cells to be included in the addition process.
Take a look at the image to the right. If you wanted only to add together values that are greater than five, you could write the SUMIF formula as follows:
As the cells A2 and A5 contain a value that is greater than five, they'll be the only ones added together by the formula, resulting in a value of 17.