Using the SUM formula this way will allow your data tables to grow and include any new items by running totals.
- Type SUM function with a range that contains only single cell =SUM(C3:C3)
- Make range’s first cell absolute by clicking on it and pressing F4 key =SUM($C$3:C3)
- Copy down the formula all the way down =SUM($C$3:C8)
The trick is using a mixed reference to expand formula range cell by cell. Formula range expands by relative reference while absolute reference is locked at cell. As a result; SUM function calculates one cell more with every new cell.