Using Copy/Fill Excel

Copper Contributor

I create a pattern to fill down.  The pattern starts with 3.50%, in the next cell 3.75%.  I select both cells and then use the copy/fill tool to copy down to 7.00%.  After the fill, when I click on 6.25%, the value is rounded to 6.24999999%.  This is a problem as I am using a separate cell that may contain any one of the values listed, but of course, it doesn't work for the values that rounded down.  I am a teacher and have been teaching this lesson for 6 years.  This is a new behavior for Excel.  I am using Microsoft Office 365 Professional (Office 2021)  (our school has a subscription).  Thank you for your help.

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6 Replies


That's Floating-point arithmetic may give inaccurate result in Excel - Microsoft 365 Apps | Microsoft Learn which was in previous versions of Excel as well (and not only in Excel).  

Thanks. As I mentioned, this is a new behavior in Excel and why it starts at 6.25% doesn't make sense; I am dragging down (copy/fill) from a selection (3.5 & 3.75 are selected) so it should just continue to follow the pattern of increments at .25. What I am also noticing is that if I begin with a different value (10.5%, 10.75%) and copy down, it doesn't happen. Very odd. Thanks, again.


Excel has always behaved this way, but when exactly it occurs is hard to pin down.

In your example, enter 3.5% in F5, then enter the formula =ROUND(F5+0.25%,4) in F6, and fill down from F6.

(We round to 4 decimal places since 0.01% = 0.0001)

Sounds like something is broken. Thank you for the work around.


No, it is not broken - it is due to the way computers in general, and Excel in particular, handle fractions. We humans use decimal (10-based) numbers, while computers binary (2-based) numbers. Most decimal fractions cannot be represented exactly as binary numbers, so when converting from decimal to binary and then back from binary to decimal, tiny rounding errors occur.

Ah! Then I guess I need to let the textbook publisher know not to use fractions when wanting students to use the fill/copy tool. I for sure will let my students know to double check; they haven't learned the ROUND function yet! Thank you.