The numbers one to nine are written as words; 10 and above are written as figures.
But, to avoid awkwardness, you would write: Children in the 8-10 age group.
All numbers are written as words: a) at the start of a sentence; b) when the copy describes them as approximate (about three hundred people attended); and c) in phrases such as the Ten Commandments.
For percentages use % at all times (never per cent) in both headlines and copy.
Decimals take a full point: 12.5.
Figures greater than 999 take commas: 24,500; 1,750,000.
Age, in news reports, is usually given as a figure between commas: Joanne Bartlett, 35, whose daughter Rachael, nine, has dyslexia …
But, even in news, where age is the point of the story, the rule may be relaxed: A 90-year-old woman has climbed Everest.
In features, age is given in the most appropriate way: a thirtysomething solicitor; a local politician in her twenties; Iqbal Hussain, a youthful 65-year-old …
For money, symbols are used with figures: £100; £2.50; $5m.
Where possible, use whole figures rather than decimals – £900,000 rather than £0.9m – but use decimals rather than fractions.
Currencies are written out: The pound is falling.
Foreign currency figures should normally be followed by their sterling equivalent in brackets.
Prices from past eras should normally be followed by the present-day equivalent and/or an indication of what the price meant at the time: In 1966 a glossy magazine cost in the region of two shillings (10p) – this at a time when a woman’s disposable income was typically £9 or £10 a week.
For time, use the 12-hour clock, with am or pm close up to the figure: 11am; 6.30pm.
Dates are written thus: 10 January; 25 August 1948.
Note also: the 1990s or the Nineties (not the ’90s) and: the twentieth century. And 1785-89 (not 1785-9).
Temperatures should be expressed in celsius, with fahrenheit (note the lower case) conversions in brackets. Use without degree symbol: 23C (73F), -3C (27F) but with the abbreviated letter capped up.
To convert celsius to fahrenheit, multiply by nine, divide by five, then add 32; to convert fahrenheit to celsius, subtract 32, divide the answer by nine, then multiply by five (or use one of the many online calculators).
Measurements, except miles, pints and people’s height, should be according to the metric system, with imperial conversions in brackets.