use function 101 in your subtotal for average not including hidden rows. So,
=SUBTOTAL(101,A2:A500)

If you type =SUBTOTAL(, thin click the Fx button in your address bar, you
can click the "Help on this function" hyperlink for more options.

"QB" wrote:

I found out instead of using the sum(), I should use the Subtotal() to get
the proper value of a summation over an autofilter result.

That said, I need to get the average of a column which has an autofilter
applied, which function should I use to do this?

Thank you,

QB