presuming blanks are always in neighbouring A and B

=AVERAGE(IF(ISBLANK(B1:B4),"",B1:B4-A1:A4))

CTRL+SHIFT+ENTER it as it is an array formula



On 22 Maj, 14:56, mckzach wrote:
Greetings all,

I am working with two columns (ranges) of dates, although there are many
blank rows interspersed in both ranges. *I simply need to calculate the
overall average days elapsed between the two columns. *In other words, I'm
looking for a single result here; Col. B (End date) - Col. A (Start date) for
as many rows of dates that exist.

COL A (Start) *COL B (End)
01/05/09 * * * *02/20/09
03/12/09 * * * *03/09/09

01/15/09 * * * *01/30/09
02/19/09 * * * *02/22/09

The array formula I'm using (below) works, but is factoring in the blank
cells and is giving me a lower inaccurate result.

*{=AVERAGE((B$2:B$100)-(A$2:A$100))}

Any help at all would be appreciated.