There are different ways of writing uncertainty. The siunitx manual says "In some fields, it is common to give the uncertainty in a number in brackets after the main part of the number... Alternatively, the uncertainty may be given as a separate part following a sign."


  • 1.234(5)
  • 1.234 ± 0.005

Which academic fields use which style in their journal articles? Does it depend on the region? Is there any agreed upon standard?

  • Use the one matching the standard in your field and don't worry about the other. Ho w does one know that (5) is 0.005 and not 0.05 ? – Solar Mike Apr 9 at 5:35
  • 3
    @SolarMike presumably because the uncertainty applies to the least significant reported digit. – Maeher Apr 9 at 5:53

Yes, there is an agreed upon standard and it is specified in the Guide to the expression of uncertainty in measurement (GUM), section 7.2.2, prepared by the Joint Committee for Guides in Metrology (an ISO committee).

Both forms are equally valid, and people use them indifferently. The first form is just more compact and it is particularly useful in tables, abstracts etc.

For an uncommon usage of the first form, see also this answer of mine on Physics SE.

  • Your reference says "The ± format should be avoided whenever possible." Fascinating. – Anonymous Physicist Apr 9 at 7:17
  • @AnonymousPhysicist iirc most of the engineering texts use ± , and in some cases that is not good enough as the tolerance can be greater in one direction compared to the other... – Solar Mike Apr 9 at 7:25
  • @AnonymousPhysicist I'd say that that note is usually ignored also by those who work in the field. – Massimo Ortolano Apr 9 at 7:25

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