Never test if two values are equal with formulas like
=A1=B1
But use
=ROUND(A1-B1,12)=0
or
ABS(A1-B1)1e-12

This will get around the IEEE rounding errors

If you want to delve deeper:

Chip's clear explanation
http://www.cpearson.com/excel/rounding.htm

Floating-point arithmetic may give inaccurate results in Excel
http://support.microsoft.com/kb/78113/en-us

(Complete) Tutorial to Understand IEEE Floating-Point Errors
http://support.microsoft.com/kb/42980

What Every Computer Scientist Should Know About Floating Point
http://docs.sun.com/source/806-3568/ncg_goldberg.html
http://www.cpearson.com/excel/rounding.htm

Visual Basic and Arithmetic Precision
http://support.microsoft.com/default...NoWebContent=1

Good reading from T Valko
http://blogs.msdn.com/excel/archive/...g-answers.aspx

Others:
http://support.microsoft.com/kb/214118

http://docs.sun.com/source/806-3568/ncg_goldberg.html

best wishes
--
Bernard Liengme
Microsoft Excel MVP
people.stfx.ca/bliengme
email address: remove uppercase characters

REMEMBER: Microsoft is closing the newsgroups; We will all meet again at
http://answers.microsoft.com/en-us/o...ult.aspx#tab=4

"chitown29" wrote in message
...
In Excel 2003 and 2007, why, when adding 664,199.05 and negative
582,911.61
the answer comes out 81,287.4400000001? Why is there a 1 at the end?
This
causes issues when building formulas to control two sets of information
that
should equal one another.