The title of the post is a bit of a misnomer because the SUMIF function in Excel does not allow you to have more than condition.
Excel 2007 introduced the SUMIFS function which allowed for multiple conditions. However, if you are using any version prior to Excel 2007 or if the persons who will be using your Excel workbook will be using a version prior to Excel 2007, then the SUMIF function will throw up an error.
That is a problem a colleague faced at work. To solve this problem you can use SUMPRODUCT along with double negation. The double negation is simply two minus signs one after an another. The net effect is that it doesn’t change the value of the calculations.