Assuming no embedded blank cells, try this for last (latest) 52 week average:

=AVERAGE(INDIRECT("A" & COUNTA(A:A) & ":A" & COUNTA(A:A)-51))

To get 3 and 5 year average change 51 to 103 and 259 respectively

HTH

"Jen" wrote:

I have a worksheet that has 8+ years worth of weekly rates (which are added
to each week). I am trying to calculate the 1 year, 3 year and 5 year
averages.
I need my spreadsheet to automatically calculate the average of 52 cells so
each time I add a new weeks rate, it will change the source to read the most
current 52 weeks.
Also €“ my rates are in reverse order (oldest on top), so locking the cells
wont work.
Are there any formulas I can put in to do this?

Thank you!!