information:extraction
United Kingdom

Since the Weights and Measures Act 1985, British law defines base imperial units in terms of their metric equivalent. The metric system is routinely used in business and technology within the United Kingdom, with imperial units remaining in widespread use amongst the public. All UK roads use the imperial system except for weight limits, and newer height or width restriction signs give metric alongside imperial.

Traders in the UK may accept requests from customers specified in imperial units, and scales which display in both unit systems are commonplace in the retail trade. Metric price signs may be accompanied by imperial price signs provided that the imperial signs are no larger and no more prominent than the metric ones.

The United Kingdom completed its official partial transition to the metric system in 1995, with imperial units still legally mandated for certain applications such as draught beer and cider, and road-signs. Therefore, the speedometers on vehicles sold in the UK must be capable of displaying miles per hour. Even though the troy pound was outlawed in the UK in the Weights and Measures Act 1878, the troy ounce may still be used for the weights of precious stones and metals. The original railways (many built in the Victorian era) are a big user of imperial units, with distances officially measured in miles and yards or miles and chains, and also feet and inches, and speeds are in miles per hour.

Some British people still use one or more imperial units in everyday life for distance (miles, yards, feet, and inches) and some types of volume measurement (especially milk and beer in pints; rarely for canned or bottled soft drinks, or petrol). As of February 2021, many British people also still use imperial units in everyday life for body weight (stones and pounds for adults, pounds and ounces for babies). Government documents aimed at the public may give body weight and height in imperial units as well as in metric. A survey in 2015 found that many people did not know their body weight or height in both systems. As of 2017, people under the age of 40 preferred the metric system but people aged 40 and over preferred the imperial system. As in other English-speaking countries, including Australia, Canada and the United States, the height of horses is usually measured in hands, standardised to 4 inches (102 mm). Fuel consumption for vehicles is commonly stated in miles per gallon (mpg), though official figures always include litres per 100 km equivalents and fuel is sold in litres. When sold draught in licensed premises, beer and cider must be sold in pints, half-pints or third-pints. Cow's milk is available in both litre- and pint-based containers in supermarkets and shops. Areas of land associated with farming, forestry and real estate are commonly advertised in acres and square feet but, for contracts and land registration purposes, the units are always hectares and square metres.

Office space and industrial units are usually advertised in square feet. Steel pipe sizes are sold in increments of inches, while copper pipe is sold in increments of millimetres. Road bicycles have their frames measured in centimetres, while off-road bicycles have their frames measured in inches. Display sizes for screens on television sets and computer monitors are always diagonally measured in inches. Food sold by length or width, e.g. pizzas or sandwiches, is generally sold in inches. Clothing is usually sized in inches, with the metric equivalent often shown as a small supplementary indicator. Gas is usually measured by the cubic foot or cubic metre, but is billed like electricity by the kilowatt hour.

Pre-packaged products can show both metric and imperial measures, and it is also common to see imperial pack sizes with metric only labels, e.g. a 1 lb (454 g) tin of Lyle's Golden Syrup is always labelled 454 g with no imperial indicator. Similarly most jars of jam and packs of sausages are labelled 454 g with no imperial indicator.