Writing tip: Write 1, 2, 3. Numbers in plain language and legal prose

Writing tip: write numbers in digits (1, 2, 3) rather than words (one, two, three) unless you have a strong, specific reason to do the opposite.

In legal prose it is traditional to write every number twice, first in words, followed by the same number written in digits enclosed in brackets:
That sentence contained twenty-five (25) words.
Easy as one (1), two (2), three (3).

A student commented on legal prose, especially: "that three (3) bit. Like we never see numbers as words?? Why would that ever be clearer?"

Well, there is a reason, no doubt. In a legal document, numbers are less likely to contain mistakes if they are written twice—or at least the mistake will be obvious.

Words are the traditional way to write numbers in a document, but digits leap off the page and grab our attention. They use a different visual language, so they stand out in a sea of ABC words.

But I agree my correspondent: in most cases, outside of legal prose, one version of a number is enough. And online, digits win.

Jakob Nielsen has confirmed this: It's better to use '23' than 'twenty-three' to catch users' eyes when they scan Web pages for facts, according to eyetracking data.

Deciding when to use digits or roman letters for numbers never was straightforward. The Australian Style Manual devotes 15 pages to the issue! Nielsen suggests guidelines for web writing that differ from traditional writing style:

  • Write numbers with digits not letters, even when they're first in a sentence.
  • For big numbers, combine the two, as in 24 billion.
  • Spell out numbers that don't represent facts.

I like that. But it is never going to be entirely simple.

For example, take the phrase Write 1, 2, 3. Strictly speaking, that should be one, two, three, because those numbers don't represent facts. But the topic of this blog post is the use of digits, not just word-numbers. So I want 1, 2, 3 to stand out even though the numbers are not facts or data. Fiddly reasoning, case by case.

Also, we should make an exception for the numbers one (1) and zero (0) in isolation. The digits don't stand out because they look like an el (l) and an oh (O).

The new write-digits rule for online content will keep writers on their toes. And it's no use saying this rule only applies to online content. Mountains of documents are published both online and on paper. It's absurd to think we will have two versions of each, one for print and one for the web or intranet.

No way are we going to create two inconsistent versions of documents, one for the Web (which can be printed and converted to hard copy) and one for hard copy (which can be published online). My rule of thumb: write what works on the Web and it will work just as well on paper. So watch me use 1, 2, 3 as the default way of writing numbers, on purpose, from now on.

Style guides will need changing. And sooner or later, web rules must rule.

Jakob Nielsen's Alertbox on writing numbers, 16 April 2007


Rachel McAlpine
Rachel McAlpine

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