Words or digits?
For the most part, we use words for single-figure numbers, digits for anything above nine (ie eight, nine, 10, 11) - except with abbreviated units of measurement (eg: 3kg) and with percentages (eg: 4%).
However, in headlines we can use numerals for numbers below 10, as in Boy, 8, hurt in rollercoaster crash or Pound falls to 5-year low.
But never start a sentence or headline with digits (eg: Fifty MPs have been expelled; Four per cent of the patients have died).
The same rule works for ordinal numbers: (eighth, ninth, 10th, 11th).
Millions and billions are spelled out, except where they are used with currencies or in headlines (five million people, 10 billion grains of sand, £5m). And remember that billion is widely accepted as meaning "one thousand million" (not "one million million"). Fractions are written as words or, where appropriate, as a decimal (eg: three-quarters or 0.75).
Hours: We use the 24-hour clock (with a colon) in all circumstances (including streaming), labelled GMT or BST as appropriate. World stories put local time first, followed by conversion into GMT. Domestic stories which mention overseas local time should convert into UK time eg: The foreign secretary will leave London immediately after the cabinet meeting - arriving in Washington at 11:00 local time (16:00 BST). In a story with several time references, we don’t need to use BST/GMT on every occasion; establishing the time zone once should be enough. Also, judge whether it adds anything in a historical sense, as in: "The court heard Jones had burgled the house at 14:25 GMT in November last year."
Days: Since our international users live in various time zones, we must not use "yesterday", "this morning", "today", "tonight", "tomorrow" etc. Instead, days should be referred to by name (eg: Voting begins on Monday) - and we should not follow the American custom of omitting the preposition (eg: "Voting begins Monday"). When writing about events which have happened or are due to happen on the day a story appears, we should avoid putting the day of the week in the top four pars. If some indication of timescale is needed, use another form of words such as "within hours", "shortly", "later" or "earlier". If there is scope for confusion, include the day lower down the story.
Seasons: For similar reasons, references to the seasons should be kept to a minimum. We should not say eg: "An election will be held in the spring". Substitute with An election will be held in five months’ time - or similar.
Dates: Put the day before the month (eg: 12 April 2001). Avoid the 12/04/2012 formulation in alt tags or anywhere else, as this will be understood in the US as 4 December. Do not include suffixes after the day (eg "20th"). One exception to the general rule: in a US context, we should spell out the Fourth of July. When writing about any sporting season, or tax or financial years etc, our preferred style is 2010-11. AD, as in the year of the Lord, goes before the year (eg AD800) with no gap. BC goes after the year - eg: 100BC.
Decades: are written 1960s, 1970s, 1980s, ie with no apostrophe before the "s". But there should be one at the start of a date if you omit the century - eg: The oil crisis of ‘73 or when an adjective is attached - eg: the Swinging '60s. Digits are also used in the decades of an individual’s age (eg: Henry Higgins is now in his mid-50s).
Centuries: with an initial cap if labelled with a number (eg: 21st Century). Otherwise, lower case (eg: Scientists expect a cure for cancer by the end of the century).
Weights and measures
We should use both imperial and metric measures in most stories. Context will usually decide which measure comes first, but if the first figure is part of a quote it should be retained, with a conversion in brackets immediately afterwards.
Where instantly recognisable abbreviations exist, these should be used throughout, even at first reference. For example, the words "metre", "kilometre" are not written out in full even at first reference; use the abbreviations m and km. All numbers preceding abbreviations should be rendered as digits; where units are written out in full, our usual numbers convention is followed. There should not be a gap between number and abbreviated unit, and units of measurement do not in general take an "s" in the plural.
UK and US stories should usually use imperial first - eg: He said the first 50ft (15m) of the climb had been hard. The president’s campaign helicopter has taken him more than 2,000 miles (3,200km).
For feet and inches, use digits followed by abbreviations - eg: The hedge was exactly 9ft 4in high (2.84m).
In non-UK/US stories, metric should usually come first - with a bracketed conversion to imperial - eg: Police in France say the floods reached a peak of 5.3m (17ft 8in). Many fugitives from English justice are living along a 10km (6.2 mile) stretch of the Spanish coast.
Sometimes logic will dictate when metric should come first eg: Train speeds on the British side of the Channel Tunnel compare badly with French top speeds of 300km/h (186mph). But don’t be too literal in the conversion of an approximate figure, as in The lifeboat picked up the man about 200m (656ft) from the shore.
A nanometre is one thousand millionth of a metre. Spell it out in full at first reference; then trim to nm, with the accompanying number expressed as digit(s) eg: 6nm, 52nm.
For weights originally expressed as a precise number of stone, write out the word "stone" (never "stones") - and follow our usual convention with any accompanying number - eg: The child weighed less than two stone (12.7kg) at the time of his death; She said the company had sacked her because she weighed 15 stone (95.3kg).
But if pounds are involved you should use the abbreviations st and lb (not "lbs"), and use digits even for numbers below 10, with no gap between number and unit - eg: Charles Atlas said he had once weighed 6st 9lb (42kg).
From a gram (one thousandth of a kilogram), the abbreviation g is used at first reference and throughout. This rule applies whether singular or plural. It is lower case and there is no gap between number and unit - eg: Police say they found 30g (1oz) of cannabis in the woman’s handbag.
Tonne: Use the metric measurement rather than the imperial "ton". In reality, there is very little difference between the two. Avoid the term "metric ton", and of course the tautological "metric tonne".
For volumes, the usual approach, again, is to use both metric and imperial - eg: The tanker was carrying 30,000 gallons (136,000 litres) of petrol. (Note that "litres" is not abbreviated, because "l" looks like a number one.) However, phrases where volume and liquid are historically almost inseparable do not have to be converted - eg: He told the court his favourite pastime was to go out with his friends for a curry and a pint. Thus, a pint of beer or a pint of blood are acceptable, unconverted, in any story - though context will sometimes make a metric conversion appropriate in, say, Technology or Health.
Adjectival phrases defining areas should include hyphens in both metric and imperial measures. Always mention both; the context will determine which comes first - eg: The French fishermen denied reports that they had been operating inside the X-sq-km (Y-sq-mile) zone (note: there is no "s" on nouns used adjectivally). Elsewhere, there is no need for hyphens - eg: The UK government is calling for a ban on fishing within a zone of X sq miles (Y sq km).
Abbreviations should be used throughout. Never write "square kilometres", but always sq km. There is no acceptable abbreviation for "miles", so write sq miles (and, adjectivally, sq-mile).
Always hyphenate the adjectival, whether it is eg seven-year-old child or 100-year-old coin. Hyphens should also be included in the noun eg There are to be more school tests for eight-year-olds - though hyphens are not necessary in sentences such as The missing boy is three years old.
An age placed after a name should be sandwiched between commas eg ‘John Jones, 61, has been knighted.’
With Sports stories, be guided by the traditions of the individual sport in deciding which system of measurement should be given prominence. For a cricket match in the Netherlands, it should be imperial; for an athletics meeting there it would be metric. But conversions will always help to reach a wider audience eg: Anderlecht have signed a striker who is 6ft 8in tall (2.03m).
Football, rugby etc use digits for scores eg: Arsenal 2-3 Leeds.
Cricket uses digits for all numbers, both in stories and in summaries eg: Anderson took 3-42.
Tennis scores use digits for all numbers, without commas between sets eg: Smith beat Jones 6-4 6-7 (2-7) 7-6 (7-4). Note that tiebreak scores are inside brackets and separated by dashes.
Winning margins in matchplay golf are written in digits with an ampersand eg: Morris beat Rose 4&3.
Golf holes are referred to as the 3rd, 4th etc (not "the third", "the fourth" etc).
In Athletics events such as the 100m, where times below 10 seconds are regularly achieved, all numbers should be written as digits - and the word "seconds" need not be used throughout eg: "X took gold with a time of 9.93 seconds. In second place was Y, on 9.94. And the bronze medal went to Z, on 9.96."
Elsewhere, the first reference to a time in athletics should spell it out in full, following the usual convention with numbers below 10 eg: one hour two minutes 23.34 seconds (with no commas between units). After that, switch to a more compact style eg: 1:03:25.67.
Insert commas into numbers of four digits and above eg: "The race attracted a crowd of 65,000" - but not necessarily in athletics events eg: "A smaller crowd watched the final of the men’s 1500m" - where the figure is pronounced "fifteen hundred"). The "One" in Formula One is written as a digit eg: Formula 1 or F1.
We say: 50p; £5; £60; £3m; £500m; £6bn; £20bn; £15tn.
In UK stories (about UK firms, the UK economy etc), use pounds only in the first four paragraphs, but provide a US dollar conversion of a key figure at the earliest opportunity.
In eurozone stories (or wherever the original reporting figure is euro), use euro followed in brackets by a pound conversion of a key figure - even in the first four paragraphs.
In World stories (ie non pound, non eurozone), use US dollars, followed in brackets by a pound conversion of a key figure - again, even in the first four paragraphs. Alternatively, use the local currency and then convert to both US dollars and sterling (eg: Japan’s Nayaka has announced the worst corporate result in history, losing 40 trillion yen ($340bn; £212bn).
Abbreviations: The names of all currencies are written out in full at first reference - with the exception of the pound sterling and the US dollar, which are always £ and $. The euro is always the euro: we do not replace its name with a symbol. Otherwise, abbreviations to be used after first reference are: SFr (Swiss francs); HK$ (Hong Kong dollars); A$ (Australian dollars).
Always use Celsius, not centigrade or Fahrenheit. Contrary to our usual style with numbers, we always use digits with temperatures (eg: 8C, 10C, 42C). It may sometimes be appropriate to add a Fahrenheit conversion to UK stories eg: The temperature rose above 38C (100F) on Friday, a UK record.