Hi - Dave here.
One tricky challenge in Excel is how to sum every nth column.
In other words, how to sum values in every 3rd column, every 4th column, etc.
There are two basic approaches to this problem in Excel:
1. Extract nth values & sum the result
2. Cancel non-nth values & sum the result
The worksheet below shows approach #1:
[
download the workbook and read the full explanation]
The formula in the worksheet looks complicated. However, at a basic level, it just divides column numbers by n (3) and looks for a remainder of zero. Then it sums the associated values. The article above explains both approaches and includes the worksheet above. The formula for approach #2 will work in older versions of Excel. Download the workbook and try it out yourself.
Note: With a small set of data, you can easily enter a formula manually to sum columns as you like. The point of this example is to show how to create a general solution that will scale up to a larger set of data, and allow the value for n to be easily changed.
Excel formulas
We maintain a large list of working formulas
here.
If you need more structure, we also offer
video training.
Have a fun and safe weekend!
Dave
