It converts the boolean results of (A1:A6="b") into the numbers 0 or 1.
The same could be achieved with 0+ or 1* or even the N() function.

--
Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
Custom MS Office productivity solutions

In article ,
says...
Thank you boys and it worked a treat, but can you explain why you inserted
"--" in the formula? What is its function in the array?
Thanks


"Nick Hodge" wrote:

Rita

If the data is in A1:C6, for example, the following will sum the data in C
where A="b" and B="yes"

=SUMPRODUCT(--(A1:A6="b"),--(B1:B6="yes"),(C1:C6))

--
HTH
Nick Hodge
Microsoft MVP - Excel
Southampton, England
HIS


"rita" wrote in message
...
I want to do a sumif but using 2 criterias which appear in 2 separate
columns
within the worksheet.

a yes 15000
a no 16000
a yes 20000
a no 30000
b yes 40000
b yes 50000

In the table above, I need to know the sum of column c if I choose a
criteria found in column a and column b together.
Can you help?
Thanks
Rita