SUMPRODUCT uses cell ranges as its arguments (the parts of the formula that make it work). It multiplies the items in the cell ranges, and then sums up the result.
To create the formula using our sample grocery list, type =SUMPRODUCT(B2:B5,C2:C5) and press Enter. Each cell in column B is multiplied by its corresponding cell in the same row in column C, and the results are added up. The total amount for the groceries is $21.60.
To write a longer formula that gives you the same result, type =B2*C2+B3*C3+B4*C4+B5*C5 and press Enter. After pressing Enter, the result is the same: $21.60. Cell B2 is multiplied by C2, and its result is added to the result of cell B3 times cell C3 and so on. You can imagine, if you have hundreds (or even thousands) of rows, how much easier using SUMPRODUCT would be.
Notes:

The columns or rows must be of equal length.

If text, instead of a number, is in a cell, it’s treated as zero.