Learn Sum as Running total excel formulas

SUM (Running Total)

Using =SUM() For A Running Total

Type the formula =SUM($D$7:D7) in cell E7 and then copy down the table.
It works because the first reference uses dollar symbols $ to keep $D$7 static
as the formula is copied down. Each occurrence of the =SUM() then adds all
the numbers from the first cell down.

The function can be tidied up to show 0 zero when there is no adjacent value
by using the =IF() function.