Mark,

Take a look at this page http://www.cpearson.com/excel/rounding.htm

A good previous thread at http://tinyurl.com/8jjf4

Not directly related, but an interesting thread at http://tinyurl.com/d4475

--
HTH

Bob Phillips

(remove nothere from email address if mailing direct)

"MarkN" wrote in message
...
I am using the SUM function to add positive and negative currency values.
The
numbers are 2053.12, -1272.15, -260, -420.97 and -100. Excel returns a
result
of -0.000000000000227. The sum of the negative numbers is -2053.12 and the
positive number is +2053.12 so I was expecting 0.00.

I can use the ROUND function to sort this out but I am very interested in
knowing what causes this to happen and if there is something I can do so
that
I can just use the SUM function to return the correct result.
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Thanks,
MarkN