Please Note: This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, 2016, 2019, and Excel in Office 365. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: Rounding to Two Significant Digits.

Rounding to Two Significant Digits

by Allen Wyatt
(last updated November 14, 2020)

6

Tammy needs to round values in a worksheet to two significant digits. For instance, if a cell contains 137, it should round to 140; if it contains 0.0005937 it should round to 0.00059; and if it contains 156735.32 it should round to 160000. She wonders if there is a simple formula to round any given number to only two significant digits.

Of course, it depends on what your definition of "simple" is. Fact of the matter, though, is that there are several different formulas you can use to get the desired result. Assuming that your original value is in cell A1, you can use any of the following representative formulas:

=ROUND(A1/(10^(INT(LOG10(ABS(A1)))+1)),2)*(10^(INT(LOG10(ABS(A1)))+1))
=ROUND(A1,-(INT(LOG(ABS(A1),10))+1)+2)
=FIXED(A1,1-INT(LOG10(ABS(A1))))
=ROUND(A1,1-INT(LOG(ABS(A1))))

These formulas will work with either positive or negative values just fine. The LOG (or LOG10) function is used to determine the number of digits either to the left or right of the decimal place before the first significant digit occurs. The INT of that function actually provides a number that is one less than the number of digits required, so that is why the value has 1 added to it. We can then round using that number of digits.

If you think that you may want to use a different number of significant digits than two, then you can use either of the following formulas:

=ROUND(A1,2-INT(LOG(ABS(A1)))-1)
=ROUND(A1,2-INT(LOG10(ABS(A1)))-1)
=FIXED(A1,2-INT(LOG10(ABS(A1)))-1)

All you need to do is change the 2 to reflect any number of significant digits you want. More information about significant digits in Excel can be found here:

https://excelribbon.tips.net/T012083

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (10397) applies to Microsoft Excel 2007, 2010, 2013, 2016, 2019, and Excel in Office 365. You can find a version of this tip for the older menu interface of Excel here: Rounding to Two Significant Digits.

Author Bio

Allen Wyatt

With more than 50 non-fiction books and numerous magazine articles to his credit, Allen Wyatt is an internationally recognized author. He is president of Sharon Parq Associates, a computer and publishing services company. ...

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Comments

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What is 1 + 9?

2021-04-21 10:24:19

J. Woolley

@ALEXANDRE
For N significant digits you can format as Scientific with (N-1) decimal places. Use Home > Number on the Ribbon (or Ctrl+1).
With N=1, 0.003573267 is displayed as 3.6E-03, 140 as 1.4E+02, 367453.345 as 3.7E+05.


2021-04-20 20:33:40

ALEXANDRE CAVALCANTE

Good tip but unfortunately there is an error in the definition of significant figures. zeros to the right of a number are significant. Leading zeros are not significant and power of 10 is not significant. Therefore, as an example, the number 0.003573267 written with two signifiers would be 0.0036. The number 0.0230 has 3 significant. The number 140 (as in the example at the beginning of the text) has 3 signifiers. The right would be 14 x 10 ^ 1 or 1.4 x 10 ^ 2. The number 367453,345 with only 2 significant would be 38 x 10 ^ 4 or 3.8 x 10 ^ 5.

So, how do you represent values with 2 signifiers and the power of 10?


2020-11-15 06:32:00

Peter Atherton

=ROUND(A1,1-INT(LOG(ABS(A1)))) is the shortest formula, so that is the one I'd use.
The FIXED formula returns a text value so add a zero @ the end. =FIXED(A8,1-INT(LOG10(ABS(A8))))+0
Tony,
Copy and paste the formula into B1, and then paste B1 into whatever cell you want.


2020-11-15 06:09:53

Tony Degnen

Please disregard my previous comment, the formulae work perfectly in Excel. I didn't realise I was using an alternative spreadsheet program. Doh!


2020-11-14 20:02:51

Tony Degnen

Your tip on rounding to two significant digits produced only "err:508" when I tried it. This happened with all the alterrnative formulae you provided (e.g. =ROUND(A1/(10^(INT(LOG10(ABS(A1)))+1)),2)*(10^(INT(LOG10(ABS(A1)))+1)).
Am I doing something wrong?


2020-11-14 10:25:26

J. Woolley

Another way for N significant digits is to format as Scientific with (N-1) decimal places.


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