The Style Manual for Authors, Editors and Printers provides detailed advice on numbers. One important exception is the Museum’s preference for commas in numbers of five or more digits:
2230, 11,077 and 1,975,050
Generally, numbers up to and including nine are spelt out. Numerals are used for all numbers over nine:
There are five major galleries in the Museum.
Groups of more than 20 people need to book in advance.
For larger, more complex numbers, it is sometimes better to use a combination of words and numerals:
2.5 million
Fractions should be spelt out — two-thirds, three-eighths — in all but technical documents.
Dates and periods of time
Dates should take the following forms:
July 1962
13 November 1958
Tuesday 13 November 1958 to Wednesday 21 November 1958
Monday 21 April to Wednesday 23 April and Monday 28 April
21–23 and 28 April and 2 May
Refer to periods of time in the following ways:
early 1600s
mid-1600s
late 1600s
Note there is definitely no apostrophe before the s.
In general, include the century when referring to decades:
the 1840s
not
the ’40s
When referring to specific periods of time use the following forms:
2000–04
1920–42
1860s–90s
Financial years should be expressed in the following way:
2004–05
1998–99
Birth and death dates should not be abbreviated: 1920–1999.
Spell date out in full when using ‘from … to: from 1928 to 1939
Centuries should generally be referred to as follows:
the 19th century
the 1200s to the 1900s
An apostrophe is not needed in adjectival forms:
an 1840s engine
Use ‘about’ instead of ‘circa’:
about 1952
not
circa 1952 or c1952
Always try to avoid Latin and Greek expressions when there is an English alternative.
In exhibition text, use ‘years ago’ in preference to ‘BCE’ ‘BP’, ‘BC’, or ‘AD’. External exhibitions are sometimes an exception. Where necessary, use ‘BCE’ and ‘CE’ rather than ‘BC’ and ‘AD’.
All ages are expressed using numbers:
a 3-year-old car | a 99-year-old man |
The car was 3 years old. | a 6-month-old girl |
a 40,000-year history | The man is 98 years old. |
The nation has a history spanning more than 40,000 years. | playlunch for under-5s |
Exception: when a sentence begins with a number, always spell the number out:
Sixty-year-old Tassos retired today.
Times of day
For time, use the following abbreviated forms:
10–11am
9am–5pm
In general, use ‘noon’ and ‘midnight’: they are clearer than 12am and 12pm.
The terms ‘am’ and ‘pm’ need only be included on the last time in a series:
11 and 11.30 am, noon, 1.30, 3.30, 4.30 and 5.30 pm.
Currency
Use the following symbols and modes of presentation for Australian currency:
$ not j | $2.75 | $2.75 | $5 | $0.25 not $.25 |
Use a comma instead of a space to separate tens and hundreds of thousands:
$12,462
$12,915,365
Use the following forms for precise millions of dollars:
$8 million
$8,000,000
$8m
Note that there is no space between the ‘8’ and the ‘m’ in the last example.
Where it is necessary for clarity to show the country of origin of the currency, there is no space between the country’s acronym and the currency symbol. Australian currency is identified only with ‘A’:
A$2,000,000
US$45
Before 14 February 1966, Australian currency was expressed in imperial measure — pounds, shillings and pence. Avoid using the abbreviations s and d, but the £ symbol is the preferable form to use, particularly to avoid confusion with the weight measurement.
In historical works, quotations and other instances where conversion to decimal form would be inappropriate, sums of money expressed in imperial measure should be left unchanged. A decimal equivalent or some other comparison can be given if appropriate, but avoid trying to convert historical amounts into today’s equivalent. It is better to relate the amount to something the reader will recognise:
£5 (equivalent to the average weekly wage at the time)
Units of measurement
Choice of units
Metric units should be used for dimensions and be spelt out in full to avoid confusing an international audience:
a 60-centimetre vase
or
the vase is 60 centimetres tall
Exception: Measurements can be abbreviated where space is a problem, such as in marketing copy, in the details list relating to an object or artwork, or in tables.
If an object was constructed using a non-metric system and its measurements are integral to its identity or name, the non-metric measurement should be used in descriptive text, followed by a metric conversion if appropriate:
a 30-footer
a 6-inch (152-millimetre) gear
When listing specifications, the metric unit should be placed first:
bore, 152 millimetres (6 inches)
stroke, 229 millimetres (9 inches)
Very large and very small numbers can be difficult to grasp, so opt for the simpler expression:
20 kilograms not 20,000 grams
0.5 centimetre not 0.005 metre
1.5 billion trees not 1,500,000,000 trees
As a general rule, choose the unit so that the numerical value expressed lies between 0.1 and 1000.
Where possible, use a maximum of two decimal places:
1.52 kilograms not 1.51745 kilograms
Mass, volume and length
- Use milligrams for very small masses — 20 milligrams.
- Use grams for weights up to 999 grams — 125 grams.
- Use kilograms for weights up to 999 kilograms — 250 kilograms.
- Use tonnes for weights greater than 1000 kilograms — 6 tonnes.
- Use millilitres for volumes up to 999 millilitres — 60 millilitres; for larger volumes use litres — 20 litres.
- For engine capacity, however, cc (cubic capacity) is used — 1600 cc.
- For length, use centimetre as the basic unit — 16 centimetres.
- For lengths over 100 centimetres, use metre — 2 metres. Use millimetre for lengths smaller than 1 centimetre and in specification labels for engineering precision — 30 millimetres.
Percentages
In most cases, ‘per cent’ is spelled out in full and separated from the number by a space. In some marketing text, such as Shop sales, it is better to use the symbol, which is always unspaced:
25 per cent of the population is shorter than 1.5 metres.
30% off!
Spacing with shortened forms of units of measure
A space is usually placed between a number and the abbreviated form of a unit of measure:
20 km | 5 cm | 100 KB | 200 MB | 500 TB |
Note that 3 m means 3 metres, whereas 3m means 3 million.
With numbers and symbols, however, no space is used:
A$500 | 20c | –18 | 23ºS |
$10 | €2,500 | 20% | 3m |