Numbers up to and including ten should be spelled out in full. Numbers after and including 11 should be written using numerals.

Very large numbers should be written by combining a figure and a word such as million or billion.

Fractions should generally be written in full and hyphenated in prose. In a table or list, numerals should be used.

If a sentence begins with a number, it is preferable to spell that number out, even if it is a number above 11.

Within a single sentence, when talking about the same unit, consistency in use of written vs. numerals is preferred, even if this means disregarding the house style.

For example:

  • Imperial awarded honorary degrees to two individuals in May 2015; Professor Frank Kelly and Professor Elizabeth Simpson.
  • Schistosomiasis affects 240 million people, and each year an estimated 280,000 people die from the disease.
  • In 2014, approximately 12,000 people visited the Imperial Festival.
  • Of 50 students surveyed, just 4 reported dissatisfaction with the service provided.
  • Fifteen Imperial students participated in the competition.
  • Two-thirds of participants in the study reported reduced side effects.



The 24 hour clock should be used, with the hour separated from the minutes by a full stop. The abbreviations ‘am’ and ‘pm’ should not be used with the 24 hour clock.

For example:

  • The event begins at 11.00 and finishes at 15.00.
  • From 18.00 to 20.30, a drinks reception will be held in the Queen’s Tower Rooms.


Dates should appear before the month, and ordinals (st, nd, rd, th) should not be used.

There is no need to precede a date with the word ‘the’.

Days are generally not included in written dates, and the year should only be included when necessary for clarity or to avoid ambiguity.

For example:

  • Professor Terry Rudolph’s inaugural lecture was held on 29 October 2014.
  • The 2017 Imperial Festival will take place on 6 and 7 May.


Both ‘per cent’ and ‘%’ are acceptable, providing use is consistent throughout a piece of writing. In general, ‘per cent’ is preferable in prose, and ‘%’ is preferable in tables or lists.

For example:

  • In total, 60 per cent of Imperial responded to the 2014 staff survey.
  • The survey asked staff whether they had experienced an unreasonable level of pressure at work. Results were as follows:
  1. Never: 24%
  2. Infrequently: 30%
  3. Some of the time: 34%
  4. A lot of the time: 12%

Spans of numbers, years and time

To describe a period of time in prose, ‘from’ and ‘to’ should generally be used, with no dash. ‘Starts/begins at’ and ‘ends/finishes at’ can also be used in this context, as can ‘between’ and ‘and’.

In an advertisement, list, or where space is limited, start and end times for a period of time can be separated by an en dash (–).

To refer to an academic or financial year, separate the two years using an en dash.

To refer to a span of years, an en dash or the words ‘from’ and ‘to’ are acceptable.

When referring to centuries, it is preferable to spell out the word. When referring to decades, numerals or the spelled word can be used, as long as there is consistency throughout a piece of writing. Note that an apostrophe should not be used when referring to a decade using numerals (for example: 1980’s)

For example:

  • Imperial’s June Open Day begins at 10.00 and finishes at 16.30.
  • Careers advisors are on hand to offer guidance between 10.30 and 12.30 every Tuesday.
  • The College’s 2013–14 Annual Report and Accounts was published in December 2014.
  • During the war of 1914–18, many of the College’s buildings in South Kensington were used for war billeting of soldiers and military work.
  • (Poster) Inaugural lecture: Tuesday 7 April, 18.00–20.00.
  • Imperial’s South Kensington Campus has its origins in Prince Albert’s nineteenth-century vision of a quarter dedicated to education and culture.
  • At the end of the 1980s, the College’s merger with St Mary’s Hospital Medical School led to the formation of the Imperial College of Science, Technology and Medicine.

Distances, currency and measurements

Full and abbreviated terms for distances, currency and measurements are acceptable, provided they are used consistently. Full versions are recommended in prose, whilst abbreviated versions are suitable for tables and captions.

Full versionAbbreviation
50 square metres 50sqm
5 metres 5m
£5 billion £5bn
$10 million $10m
BUT always abbreviate metres squared 50m2

Telephone numbers

In printed material, telephone numbers should generally include the international code. For UK numbers, the first number should appear in brackets (as it is only used when a number is dialled within the UK), and spaces should be included after the area code and after the fourth number.

For example:

  • To find out more, please call +44 (0)20 7589 5111

 In online material, do not use brackets around the first number, use brackets around the international code.

For example,

  • To find out more, please call (+44) 020 7589 5111

For more information: