Weird Excel behavior

**MB421** · 05-24-2013, 11:27 PM

Hello everyone!
Here's a weird one for you guys. I'm working on a spreadsheet where one formula is killing me and it it's probably the first thing you learn to do with Excel. For some reason it's not working.

Cell A1 = 1, Cell B1 = 1.0001, Cell C1 = A1-B1

I've been trying to figure this out for days now and am starting to question my sanity. Excel gives me -0.000099999999999989 as my answer. Any idea why it rounds this out to that? Isn't the answer supposed to be -.0009999....(all 9's)? Where does that 8 come from?

**Jarko28** · 05-24-2013, 11:32 PM

post a sample book

**MB421** · 05-24-2013, 11:52 PM

Jarko28
Re: Weird Excel behavior

post a sample book

Here you go. Thanks for looking by the way.

**abousetta** · 05-25-2013, 12:06 AM

I've seen this come up several times from Excel users. I don't know all the details, but here is Microsofts explanation and workaround (http://support.microsoft.com/kb/214118?wa=wsignin1.0).

abousetta

**MB421** · 05-26-2013, 10:29 PM

Originally Posted by abousetta

I've seen this come up several times from Excel users. I don't know all the details, but here is Microsofts explanation and workaround (http://support.microsoft.com/kb/214118?wa=wsignin1.0).

abousetta

Thanks for the link. This answered my question.

**MrShorty** · 05-25-2013, 12:32 AM

Correct, that is standard floating point arithmetic "round-off" error. Not unique to Excel, either, it shows up in one form another in every program that does math. The key is to learn the skills and strategies for minimizing round-off error.