COUNTIF to compare one range versus another range

[Phil]

Okay I know how array formulas work but I'm having trouble with the
following. I want to count the number of times each value in column D
is less than each corresponding value in column B. What I have is

{=COUNTIF(D2100, "<B2:B100")}

but it doesn't work (it always returns 0).

Any ideas?

 

[Don Guillett]

try this NON-array entered formula
=SUMPRODUCT((d7:d18<b7:b18)*1)

 

[JE McGimpsey]

One way (array-entered):

=SUM(--(D2100<B2:B100))

 

[Phil]

Wow thanks guys! I spent about an hour trying to figure this out.