Preview in Formula Bar Showing Different Value than Cell

willynilly21  In order to give you more useful response we really need to know the exact formula you have and what the sheet is saying and ideal just have a copy of that sheet uploaded for us to look at.  It is very hard to speculate what is going on but I will throw a couple of things out there.

One possibility is that when you hover you are only see the result of part of the calculation.  For example:

=SIN(PI()/2)*3

if you hover over the SIN you will get an answer of 1 but that is only for SIN(PI()/2) and doesn't include the *3.  You can highlight the contents of the whole formula and hover to see if you still get only 1.  

Another option is to use the Excel Labs plug in which has a debug feature that will 'walk' through the calculation:

This shows the drop down for plug ins and the plug in you need to install.  Then in the side bar select the "Advanced formula environment" and you will get something like this:

note I had to chang PI() to RADIANS(180/2) because the tool apparently didn't like PI()