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


  • 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