When your number’s up
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There are different conventions that you can follow when presenting numbers and measurements in a document. There is no single correct method, but observing some generally accepted principles will make your documents clearer for the reader, and will present your organisation in a more professional light.
If your company already has an agreed style guide, you should follow that. But the following tips can help.
Words or numerals?
Most style guides suggest spelling out lower-value numbers in words, then switching to numerals at a certain point. But where this switch occurs can depend on the nature of your document. For a general text that is predominantly narrative and contains relatively few numbers, you might use words for values up to one hundred:
Lady Gaga will turn twenty-eight next March. (Don’t forget the hyphen.)
There are 366 days in a leap year.
Similarly for ordinals:
You are the fiftieth person to trip over that extension cord!
Lady Gaga’s plane will be the 112th flight to land this week.
In a more statistical document, or one intended for a scientific or technical audience, you could spell out values from one to nine, changing to numerals at 10:
The company has two financial goals this year: a 40 per cent increase in turnover and a 10 per cent reduction in costs.
or:
... a 40% increase in turnover and a 10% reduction in costs.
Commas or spaces?
Separating numbers of five or more digits makes them easier to grasp quickly:
7 865 000 or 7,865,000 rather than 7865000
Spaces are now more common than commas, particularly to avoid confusion in those countries where the comma is used as the decimal point. Larger numbers can be partly spelt out, for example:
3.25 million rather than 3 250 000 or three million, two hundred and fifty thousand
Fractions
Use a hyphen for approximate fractions:
Three-quarters of the students went well in the exam.
If using numerals, try to use the fraction bar (available on the symbols menu in Microsoft Word), rather than the forward slash, to avoid confusion:
Stir in 1¾ cup sugar and ½ cup water.
Rather than:
Stir in 1 3/4 cup sugar and 1/2 cup water.
Starting a sentence
Don’t start a sentence with a numeral.
Avoid: 50 per cent of the penguins were eating sardines.
Use: Fifty per cent of the penguins were eating sardines.
or: Half the penguins were eating sardines.
More information
For further guidance on expressions of time, currency, spans of numbers and mathematical equations, we recommend the Style manual for authors, editors and printers (sixth edition), published by John Wiley & Sons.
