Excel and rounding problem

  Neill 19:08 09 May 03
Locked

Question from a work colleague.
Calculation with Excel has a different answer to calculation done on a calculator.
A1 to L1 has the 12 months. A3 to L3 has various percentage figures that add up to 100%. For example, A3 has 8.5%, B3 has 10.5%, C3 has 11.5%; the rest across to L3 are all around the 10% mark but all twelve add up to 100%. In cell N5 (the target) is a figure of 3254. In A5 is =$N$5*A3, in B5 is =$N$5*B3, in C5 is =$N$5*C3 and so on across to L5.
In A5, the result is 276.59, 227.78 in B5 and so on. The addition of the A5:L5 is 3254.
These cells (A5:L5) are referred to in A7:L7. A7 has =A5, B7 has =B5 etc across to L7 and are formatted to Number with 2 decimal places. The total of this row is 3254 because, I believe, Excel calculates a number based on its stored value not the value you see.

In row 9, A9 to L9 also references A5 to L5 so A9 has =A5, B9 has =B5
Now if cells in A9:L9 are formatted to Number with no decimal place (A9 now has 277 instead of 276.9, B9 has 228 instead of 227.78). Now if that row is totalled =Sum(A9:L9) the answer is 3254.
Now if we just type the numbers from row 9 into row 10; i.e A10 has 227 and B10 has 228 etc and add them up with a calculator we get 3256, a difference of 2.

Now he wants the figures in row 9 to add up to the target figure (N5) with no variance when checked with a calculator.

Any help would be gratefully received. I could email you the simple spreadsheet if that helps. Neill

  VoG™ 19:17 09 May 03

Thanks for all that detail - makes a pleasant change!

I still think that I need to see the spreadsheet. I'll send you a message......

  VoG™ 09:04 10 May 03

Having looked at the spreadsheet I can see what is going on. As you say, Excel uses its stored value, not that displayed.

To get agreement between the Excel displayed value and a calculator value, you have to use Excel's ROUND function instead of changing the display settings.

Thus, as in the example that I've mailed back to you, use

=ROUND(A8,0)

etc along to =ROUND(L8,0)

Then =SUM(A26:L26) gives 3256 (which is correct).

There are issues of accuracy with Excel but only with numbers with many digits (>17 from memory) but for most applications, Excel gets it right, even if the result is not quite what you expect!

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