SUMIF is a formula that looks at a range of data and will sum only the specified value of that range for you. Here is an example:
=SUMIF($A$2:$A$11,E2,$C$2:$C$11)
This formula is looking at a range of values. You then give it the value that you would like to get the sum of and finally give the formula the range of cells that the values to sum up are in.
We have our customer names in the first column which is our range of values. We want to find the sum of Jason’s Total, so we tell the formula to look at E2. We then select the range of totals.
DiG with Data 