Dav,

Nice. May suggest using MOD simplifies it a bit.

=SUMPRODUCT((C18:C226)*(MOD(ROW(C18:C226)-5;13)=0))

Jack Sons
The Netherlands


"Dav" schreef in bericht
...

If you wanted to just put a formula in to calculate the sum of every
13th row, you could use the following if your data is in column c.


=SUMPRODUCT((C18:C226)*((INT((ROW(C18:C226)-5)/13))=((ROW(C18:C226)-5)/13)))

row returns the row number
int truncates the number looses the decimal places

as you want every 13th row starting at row 18 and you wish to count
this row. this number divided by 13 is equal to int(number/13) every 13
rows, but as you want to start with row 18 we have to subtract 5
(18-5=13!)

Sumproduct sums when this is true so sums every 13th row!

Regards

Dav


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