Thanks macropod, Dana DeLouis, Niek Otten, and ~L for your quick responses.
Evidently even though Excel allows the selection of 30 digits display to be
made, it only uses 15. My mistake before when I said 12. What that means to
me is that if the result of the cell formula is one third, that it will
display as 0.333333333333333000000000000000 and only 15 digits will be used
in any further calculations. I do see that there are several packages that
can be downloaded and promise to allow greater precision calculations under
Excel. I'll research them This does leave one question in my mind. Why would
Excel allow the display of 30 digits when it just plugs in zeros for the last
15?



"~L" wrote:

Precision as displayed means that what you see is where excel stops
calculating... hopefully you have a backup of the file from before you turned
that on or can recalculate the results with it off!

The way to display all 30 digits of precision is to format the cells as a
number with 30 as the number of digits.

Select the cell or range of cells, press CTRL+1, go to the number tab,
choose 'number' from the list and change the decimal places box to 30.

"ACRhyne" wrote:

I would like to do calculations in my spread sheet with 30 digits precision.
I figure this is possible because the number display allows 30 digits. I went
through the help function, and selecting the Precision as Displayed option
under the Tools, Options, Calculation tab make no difference. Excel still
rounds off at 12 digits. How do I get higher precision calculations?