Incorrect Sum

[Guest]

I am having a problem summing a column of numbers. These numbers are both
negative and positive numbers. When I sum the numbers it comes to zero.
This is correct, but when I reformat and take out a 30 decimal places I
suddenly start getting numbers starting at about the 12th decimal place.

These numbers are dollar amounts. I know they don't go beyond 2 decimal
places. I've hand entered them. When I take all of the numbers out 30
decimal places, nothing shows up. It only does it on the sum.

I tried summing only the negative numbers and postive numbers separately it
works then, but I can do it this way for what I need to do.

I've tried a bunch of things.

Thanks
Bill

 

[Dave Peterson]

Take a look at Chip Pearson's discussion why this happens:
http://www.cpearson.com/excel/rounding.htm

And look at J.E. McGimpsey's workarounds:
http://www.mcgimpsey.com/excel/pennyoff.html