Get relative row numbers in range
To get a full set of relative row numbers in a range, you can use an array formula based on the ROW function. In the example shown, the formula in B5:B11 is:
Note: this is an array formula that must be entered with Control + Shift + Enter. If you're entering this on the worksheet (and not inside another formula), make a selection that includes more than one row, enter the formula, and confirm with Control + Shift + Enter.
This is formula will continue to generate relative numbers even when the range is moved. However, it's not a good choice if rows need to be sorted, deleted, or added, because the array formula will prevent changes. The formula options explained here are will work better.
How this formula works
The first ROW function generates an array of 7 numbers like this:
The second ROW function generates an array with just one item like this:
which is then subtracted from the first array to yield:
Finally, 1 is added to get:
Generic version with named range
With a named range, you can create a more generic version of the formula using the MIN function or the INDEX function. For example, with the named range "list", you can use MIN like this:
With INDEX, we fetch the first reference in the named range, and using ROW on that:
You'll often see "relative row" formulas like this inside complex array formulas that need row numbers to calculate a result.