Numbers

The formatting of numbers is one of the key areas to check when copy editing a text – particularly in technical and professional documents. Here, consistency is the most important criteria to apply. It will look careless and sloppy if you format numbers in different ways in the same text.

While style guides vary to some degree in what they recommend for number formatting in different contexts and countries, for the most part the styling of numbers has been uncontroversial. More recently, however, the debate over when to use numerals and when to spell out numbers has become rather passionate.

Traditional style guides recommend that you spell out numbers below double digits (or even triple digits!) They argue that single numerals can be lost in the text or mistaken for letters. The Australian practice in recent decades has been to spell out ‘one’ to ‘nine’ in body text and use numerals for ‘10’ and above.

There is certainly evidence that people with low vision can have trouble distinguishing a 1 from a capital I, especially in a sans serif font. So this is something to factor into branding decisions.

But recent studies have also shown that numerals are in fact easier to process than their spelt-out forms. So increasingly, style guides are shifting their recommended position in favour of numerals in body text, particularly when read on screen.

Of course, there will be times that you will need to spell out numbers for clarity or legibility. The ASG outlines a contemporary approach, drawing from the latest research.