Microsoft Excel’s New Math

Oops… did you want the RIGHT answer to that question?

We tend to trust numbers that spit out of spreadsheets, right?  I mean, computers are objective and trustworthy!

Not so much.  Excel 2007 has a major bug.  If you multiply 850 times 77.1, the answer comes out to be 100,000.

Maybe it’s time to update Pierre Gallois’ famous quote:

“If you put tomfoolery into a computer, nothing comes out of it but tomfoolery. But this tomfoolery, having passed through a very expensive machine, is somehow ennobled and no one dares criticize it.”
- Pierre Gallois

How about ..."And even if you put good numbers into Excel, tomfoolery may still come out.”

Even my old slide rule, with its 3-sig limited accuracy, delivers 65,5xx… a much smaller error, and easy enough to resolve to the full number with a couple more steps.

Updates: 

  • In the comments Ed posted a very good link below to Joel On Software Explaining the Excel Bug - especially interesting because Joel worked on early versions of Excel.
  • and Mark at Good Math, Bad Math, discusses The Excel 65,535=100,000 Bug and floating-point operations as related to display and printing.

Posted by George on 09/25/07 at 08:42 AM
Geeky • Software •

  1. You’ve stumbled on the postmodern edition of Excel that accompanies Wikipedia. That code wasn’t supposed to be public, but it escaped. Software wants to be free.

    I’ve been telling you all along that subjective truth is where it’s at.

    Posted by Ted  on  09/25/07  at  02:09 PM

  2. Link to a very good explanation of the bug ...

    http://www.joelonsoftware.com/items/2007/09/26b.html

    Posted by EdK  on  09/27/07  at  08:32 PM

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