Numbers in business and technical writing

When to use words or numerals for numbers

In business writing, a generally accepted rule is to spell out numbers from one to nine and use numerals for 10 and above. Some organisations change at 11 rather than 10.

Numerals are usually used in scientific and technical writing, and increasingly I am seeing some organisations use numerals in all documents. Maybe this is a new trend.

If you follow the one-to-nine rule, treat ordinals (first, second, 10th) the same way.

She came third in the race.
Her friend came 44th.

If there is a small and large number in the same sentence, some people use numerals for both numbers, but others retain the normal convention.

She wore 7 bracelets and 14 necklaces.
She wore seven bracelets and 14 necklaces.

We don’t usually use numerals for:

• Fractions

one-third, three-quarters (note the hyphens)

• Numbers at the beginning of a sentence (I wonder if this rule is changing because I see sentences starting with numerals.)

Twenty-five people are expected.

How to write large numbers

There is no uniform agreement about how to write large numbers.

• Four-digit figures have either a comma or no comma.

5000 or 5,000

• You can use spaces or commas to indicate large numbers.

10,000 or 10 000

• When writing about millions and billions, use words or abbreviations. Under ISO 1000:1992/Amd 1:1998, millions are represented by M, but according to the Australian Government’s Style manual (2002), m is preferable to M as long as the context is clear.

10 million (10m) or 10 million (10M)
10 billion (10bn)

$96 million
$96m or $96M

When to use numerals

Use numerals for percentages and degrees. The standard convention is to use percent/per cent in the body of the text and the symbol (%) in brackets and tables. However, increasingly, some writers choose to use the symbol (%) throughout their writing.

Other numeral usages in business writing include:

• Decimal points

8.6

• Page numbers

page 2 (or you can abbreviate: p2)

• Years

2019 (There’s no universal agreement about how to write dates. Read my post on Dates in business writing.)

• Money

$500 (There’s no universal style for writing about money. Read my post on How to write about money in business writing)

• Ratios

3:5

• Time

8am (or 8 a.m.)

Abbreviations with numbers

We often use abbreviations with numerals of time or measurement. Whether you have a space or no space with time and measurement abbreviations is a style choice. The same applies to full stops in abbreviations (8am or 8 a.m.).

55 metres 55 m or 55m
28 grams 28 g or 128g

The abbreviation of a unit name takes an initial capital if it is named after someone, but you don’t need an initial capital for the full name.

watts (W)

Most other abbreviations are lower case. ‘L’ is an exception. It is capitalised to avoid confusion with ‘1’.

Some abbreviations mix lower case and capitals.

mL

Unit abbreviations and symbols remain unchanged in the plural.

1 km or 1km (space or no space)
58 km or 58km

More SI units.

Hyphens with numbers

The Chicago Manual of Style has an excellent hyphenation guide (7.89). Here are a few points (abbreviated and modified):

• Age terms: hyphenated in adjective and noun form

a three-year-old
a five-year-old child

• Fractions: hyphenated in noun, adjective and adverb form

one-half
a two-thirds majority

• Money: hyphenate before a noun but leave open after when using words, but with symbols, leave open in all positions except in number ranges

a five-cent raise
$30 million loan
a $50-$60 million loss

• Number + noun: hyphenated before a noun, otherwise open

a 250-page book
a book with 250 pages
third-floor apartment
apartment on the third floor

• Number + percent: only hyphenated between number ranges

a 30-40 percent increase

PS The words ‘numbers’ and ‘numerals’ are used interchangeably, but there is a difference. A number is a concept and a numeral expresses that concept in writing, irrespective of whether you write ‘five’, ‘5’ or the Latin ‘V’.

In practice, though, I think we often use ‘numerals’ to refer to numbers expressed in digits. And sometimes we just use the term ‘numbers’!

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