Perhaps the values in G1:G20 look like numbers, but are actually text
values, so the SUM function cannot add them. You may need to format
the cells as General or Number, then click on an empty cell somewhere
and <copy, then highlight G1:G20 and Edit | Paste Special | Values
(check) | Add (check) | OK and <Esc. This will convert them to
numbers.

Hope this helps.

Pete

On Oct 24, 12:58 am, Brwnize1
wrote:
I know this is probably simple, but can someone tell me why a simple sum
function [e.g. =SUM(G1:G20)] would return a value of 0?