Excel's precision is 15 decimal digits. See

http://support.microsoft.com/kb/78113

There are add-ins available to calculate with more digits. Be careful: you
can't process those numbers with standard Excel formulas and functions.

Look he

http://digilander.libero.it/foxes/MultiPrecision.htm
and
http://precisioncalc.com/index.html

But if you just need more digits for any identifiers, such as credit card
numbers or product id's, store them as text, not as numbers


--
Kind regards,

Niek Otten
Microsoft MVP - Excel


"brianpo" wrote in message
...
Multiplying 111111111 by 111111111 in Excel 2007 results in
12345678987654300, which is obviously wrong.
Is there a way to improve the accuracy of results over 15 digits?
Thanks, Brian