2.10 Numerals and units of measurement

(a) Hyphenate compound cardinal and ordinal numerals from twenty-one (twenty-first) to ninety-nine (ninety-ninth) when written out:

• There are twenty-nine members on the committee.

(b) Hyphenate a compound adjective in which one element is a cardinal or ordinal numeral and the other a noun:

• a five-kilometre trek
• a first-class coach
• a $4-million project
• a two-car family
• a third-rate play
• a 60-W bulb

Do not hyphenate before a symbol that is not a letter, and do not hyphenate a modifier in which the numeral, written in full, is itself a compound:

• a 100 °C thermometer
• a two hundred and fifty hectare farm

In cases such as the second example, use the abbreviated form (a 250-ha farm) if at all possible.

See 5.05 Adjectival expressions and juxtaposed numbers for further information.

(c) Do not hyphenate a possessive noun preceded by a numerical expression:

• one week’s pay
• 40 hours’ work
• three weeks’ vacation
• 10 months’ leave

(d) Hyphenate expressions of time of day as follows when writing out numerals:

• eight-thirty
  • eight thirty-five
• four-twenty
  • four twenty-six

5.05 Adjectival expressions and juxtaposed numbers

Normally, for numbers used in adjectival expressions, follow the rule given in 5.01 Introduction, i.e. write out those from one to nine and use numerals for the rest:

• seven-hour day
• two-metre-wide entrance
• a 10-year-old boy

If the unit is represented by an abbreviation or symbol, use numerals (see 1.23 The International System of Units (SI)):

• a 2.36 m high jump
• three 5-L containers

or

• three 5 L containers

Do not use a hyphen between a numeral and a non-letter symbol:

• a 90° angle
• four 100 °C thermometers

When a number immediately precedes a compound modifier containing another number, spell out the first or the smaller number:

• ten 34-cent stamps
• 15 one-litre jugs
• two 10-room houses
• 120 eight-page reports

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