Wrong(?) calculation result in Excel

[Jim]

While my calculator gives the correct result for
111,111,111 X 111,111,111 (12345678987654321, when I use
Excel for the same calculation, the result I get is close,
but not exact--12345678987654300.

Can anyone help explain what's happening in Excel?

Many Thanks,
Jim

 

[Andy B]

Hi

Go to Excel help and do a search for Specifications.
In there you will see that Excel only calculates to 15 digits of precision.
I'm sure others will post quoting the IEE specification that Excel works to.
It's very interesting and well worth a read.

 

[JE McGimpsey]

An excellent treatment is

http://cpearson.com/excel/rounding.htm