# Sum every 3 cells

To write a formula that will sum "the next 3" cells each time it's copied, you can use the OFFSET function. In the example shown, the formula in O5 is:

*Note: the point of this formula is to eliminate the manual task of entering ranges manually with a single global formula, at the cost of a more complex formula.*

### How this formula works

At the core, the OFFSET function delivers a range of 3 cells to SUM, which returns a summed result.

The arguments for OFFSET are provided as follows:

For **reference** we use the first cell in the data range, B5, entered as a mixed reference (column locked, row relative).

For **rows**, we use 0, since we don't need to change rows.

For **cols**, we use the expression:

This part of the formula figures out how many columns from the starting reference to offset. In O5, the offset is zero, in P5, the offset is 3, and so on.

Finally, **height** is input as 1 and **width** is input as 3, since in this case we always want a 1 x 3 range of cells.

*Note: change 3 to the multiplier you need, shown as "n" in the generic form of the formula above.*

## Excel Formula Training

Formulas are the key to getting things done in Excel. In this accelerated training, you'll learn how to use formulas to manipulate text, work with dates and times, lookup values with VLOOKUP and INDEX & MATCH, count and sum with criteria, dynamically rank values, and create dynamic ranges. You'll also learn how to troubleshoot, trace errors, and fix problems. Instant access. See details here.