Comments on: Excel 2007 bug shows wrong answers to simple multiplications

By: Adam Vero

Adam Vero — Wed, 05 Oct 2011 08:40:12 +0000

In your example, if the column for “diff” is only showing 2 decimal places but storing more, then this could easily be correct, ie 5.0021 * 100 = 500.21

Have you tried changing the format for the diff column to show more decimals?

Is the formula for diff = round price – price?
Is round price actually rounded using a ROUND[DOWN][UP] formula? I guess the “rounding” of “U-Next $” means up to the next whole dollar ie to use ROUNDUP(New Price,0)?
Is price stored to two decimal places as it is displayed?

I would be very surprised if this was actually a bug in the calculation engine, and it does not look likely to be a floating point inaccuracy either, at face value.

By: Syed

Syed — Wed, 05 Oct 2011 07:20:38 +0000

I also got same problem on Excel 2010 but this with simple multiplication rounded to 2 decimal places

Qty Price Secmast Spread New price Rounding Round price Diff Mark param
100.00 16600.00 165.07 1.03 170.02 U-Next $ 0.98 171.00 5.00 500.21
100.00 2900.00 28.01 1.02 28.57 U-Next $ 0.43 29.00 0.00 0.02
100.00 1200.00 11.69 0.00 0.00 -12.00 -1200.00

The param cell here has a formula to calculate Qty*diff i.e 100.00*5.00.

Any solution for this ?????

By: Adam Vero

Adam Vero — Thu, 19 May 2011 07:50:32 +0000

Glad to see you fixed it.
A cheaper alternative to new batteries might have been a good old pencil and paper, of course!

By: paul

paul — Wed, 18 May 2011 19:58:40 +0000

never mind. I replaced the batteries in my TI 89 calculator and now it agrees with excel.

By: paul

paul — Wed, 18 May 2011 19:41:36 +0000

posted on May 18, 2011.

I am getting the wrong answer averaging three numbers when using Excel 2007 (12.0.6550.5004) sp2 mso 12.0.6554.5001) part of microsoft office home and student 2007

when i simply try to take the average of three numbers in cells C5, C6, C7.

2.41
2.47
2.34

my equation in cell c8 is (C5 + C6 + C7) / 3
The answer from excel = 2.40666667

On my calculator i type (2.41+2.47+2.34)/3
and the calculator gives 2.41666667

I tried using Round (cell,2) and any other function I could find… but nothing works.

This should round to 2 decimal places as 2.42 not 2.41 which is what excel gives me.

By: Adam Vero

Adam Vero — Wed, 31 Oct 2007 23:13:47 +0000

Sorry Tom, but that's not a bug of the same class at all. That is simply a number which cannot be properly represented in floating point notation within Excel as it is too long. It loses the least significant part of the number when converting for display, as Excel can only handle up to 15 significant digits, which is well documented. There are many examples of this type, such as the simple 543,215,432,154,321/2 which yields 271,607,716,077,160 with no .5 on the end. Multiplying the result by the original denominator actually gets the correct number back, Excel is doing some clever work behind the scenes to keep reality together. Even if you copy and paste special > values then multiply that back up, you get the right answer. Some functions like ROUNDUP do choke on this and give the wrong result, though, since it cannot see any decimal part and assumes this really is an integer. As I said, you are working near the upper limits what Excel can handle here. I think these kind of 'errors' are of such small magnitude (1 in hundreds of millions of millions) that people are more ready to accept them than the lowly, domestic sized numbers involved in the actual display bug around 65,535.

By: Tom Nash

Tom Nash — Wed, 31 Oct 2007 22:47:30 +0000

A variation of this error is the display of the following division:
517,924,440,926,512/ 3 displays 172,641,480,308,837

Multiplying 172,641,480,308,837 *3 gives a value of
517,924,440,926,511.

By: Excel 2007 calculation bug fix released after two weeks « Getting IT Right

Excel 2007 calculation bug fix released after two weeks « Getting IT Right — Wed, 10 Oct 2007 17:01:13 +0000

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