The presentation of numbers in a document can sometimes leave a proofreader at sixes and sevens. Even if you are not following a specific house style in your work, it can be invaluable to lay down a few rules in your mind before beginning so that the style of numbering in your document feels consistent throughout.
In general, numbers can be expressed in two different ways:
- Arabic numerals: 0 1 2 3 4 5 6 7 8 9
- words: one, two, three, four, five, etc.
Which of these you choose may count on the feel you want to give your document; for example, if writing descriptive prose, numerals may feel interruptive and so you may opt to write all numbers out as full words. On the other hand, a technical or instructive document may benefit from the clarity of numerals. Many publishers use the following (or a similar) rule of thumb: full words from one to nine, and numerals for 10 or above.
It is common to see chapter numbers expressed either as numerals or as words; whichever you choose, you should ensure it is consistent. (Also take care to check the number of chapters; to opt for full words and then find yourself using references such as ‘Chapter Two Hundred and Seventy-Seven’ can be impractical!)
Even when following one of these blanket rules, certain exceptions can arise; here are some of the most common.
The following should usually be expressed as numerals:
- units (15 cm, 30 km, 64 GB)
- year dates (2015)
- page references (p. 225)
- names or trademarks registered in that style (50 First Dates, 7 Up)
The following should usually be expressed as words:
- numbers that begin a sentence
- names or trademarks registered in that style (Ocean’s Eleven, Nineteen Eighty-Four)
A few other useful numeric rules to remember…
Compound numbers, when written out, should be hyphenated:
- but one hundred and forty-four
Commas can be used in prose or non-technical texts in numbers of four figures or more:
In technical texts you can opt to remove the comma completely or replace it with a space (for numbers above four figures using a space can be clearer):
- 51357 or 51 357
- 10 000 000
Commas should not be used in numbers of four figures or more in:
- years (2013)
- page/chapter/line numbers (page 3145)
- house or building numbers (1572 Main Street)
When expressing a numeric range, use ‘from X to X’ or an en dash (X−X):
- from 1914 to 1918
- pages 303−306
Never use a combination of this style (e.g. from 1914−1918). The phrase ‘between 1914−1918’ is very common but also incorrect.
Also never use elision in number ranges:
- they ranged in cost: £1—2000 ( this means from £1 to £2000; must write £1000−2000)
Plural numbers, as with other plurals, do not need an apostrophe:
- sixes and sevens
- in his fifties
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