11 Numbers and dates

11.2 Numbers with units of measure

11.2.1 General principles

Generally speaking, figures should be used with units of measurement, percentages, and expressions of quantity, proportion, etc.:

a 70–30 split
6 parts gin to 1 part dry vermouth
the structure is 83 feet long and weighs 63 tons
10 per cent of all cars sold

Note that per cent rather than % is used in running text in non-technical work, and that US English has percent, closed up.

Use figures, followed by a space, with abbreviated forms of units, including units of time, and with symbols:

 winds gusted to 100 mph 250 bc 11 a.m. 13 mm

although % is commonly closed up, contrary to SI guidelines.

11.2.2 Singular and plural units with numbers

Note that units of measurement retain their singular form when part of hyphenated compounds before other nouns:

 a five-pound note a two-mile walk a six-foot wall a 100-metre race

Elsewhere, units are pluralized as necessary, but not if the quantity or number is less than one:

 two kilos or 2 kilos three miles or 3 miles 0.568 litre half a pint

For a fuller discussion of scientific units see Chapter 14. Do not add ‘s’ to unit symbols (cm, ml) in scientific work; see 14.1.3 and 14.1.4.

11.2.3 Currencies

Amounts of money may be spelled out in words with the unit of currency, but are more often printed in numerals with the symbols or abbreviations:

 twenty-five pounds thirteen dollars seventy euros £25 \$13 €70

Round numbers lend themselves to words better than do precise amounts, though even these may need to be spelled out where absolute clarity is vital, as in legal documents. For amounts of millions and above, and for thousands in financial contexts, it is permissible to combine symbols, numerals, words, and abbreviations, according to the conventions of the context in which they appear: £5 million, US\$15 billion.

Where symbols or abbreviations are used, such as £ (pounds), \$ (dollars), € (euros), ₹ (rupees), they precede the figures. As several countries use the dollar, if there is any ambiguity use the accepted prefix (A\$, US\$). There is no space after symbols, but some styles use a space after abbreviations; this is acceptable if imposed consistently within a work:

 £2,542 £3 m \$4,542 €11.47 m

Use 00 after the decimal point only if a sum appears in context with other fractional amounts:

They bought at £8.00 and sold at £11.50

Amounts in pence, cents, or other smaller units are set with the numeral close up to the abbreviation, which has no full point: 56p or 56¢ rather than £0.56 or \$0.56. Mixed amounts do not include the pence/cent abbreviation: £15.30 rather than £15.30p.

Amounts in pre-decimal British currency (before February 1971) are expressed in pounds, shillings, and pence—£.s.d. In Oxford style these are italic with a normal space separating the elements:

Income tax stood at 8s. 3d. in the £
The tenth edition cost £1 10s. 6d. in 1956

Other styles render them closed up, in roman with full points:

The statue was sold at auction for £76.10s.9d. in Manchester

The international standard three-letter currency code (ISO 4217:2008) is used in trade, commerce, and banking, and the commonest currencies are well known enough to be used without explanation even in lay texts; the amount is prefixed by the code and a normal space: GBP 500; EUR 40,000; USD 1 million. Less familiar currencies will need explanation at first mention: Macanese pataca (MOP) 1600.