Variable row number in Sum($A$1:A10) formula

[Migo1]

I need to be able to change the length of the string of numbers in a column
being added using the Sum formula such as: =Sum($A$1:A10), where A10 is a
variable adjusted by a reference to the number of rows to add in an different
cell (C1).
For instance, if C1 is the reference cell and C1 = 20, the the fomula should
automatically change to =Sum($A$1:A20).
How can this be accomplished?

 

[Gary''s Student]

=SUM(INDIRECT("A1:A"&C1))

 

[Gord Dibben]

=SUM(OFFSET(A1,0,0,C1,1))

Entered in B1


Gord Dibben MS Excel MVP

 

[T. Valko]

Another one...

=SUM(A1:INDEX(A:A,C1))

If C1 is an empty cell the entire range will be calculated.