Quick answer: The UK never went metric on a single day. The switch began on 24 May 1965, when the government backed a ten-year move to metric for industry. Packaged goods had to be sold in metric from 1 October 1995 and loose food from 1 January 2000, while miles, draught pints and the troy ounce were kept.
Many people assume Britain “went metric” at the same moment it went decimal in 1971, or that Brussels imposed it overnight. The real story is a slow, uneven shift spread over more than a century, with long pauses and a few reversals. The timeline below sets out the key dates, and the sections after it explain what each one changed. For how the two systems sit side by side today, see our overview of the UK measurement system.
Did the UK ever officially go metric?
Partly. Metric is the legal system for trade, but the UK never had a single changeover day. Since 2000, almost everything sold by weight, length or volume must be measured and priced in metric units, with imperial allowed only as a secondary figure. Outside trade, people are free to use whatever units they like, and road signs were never converted.
That makes the UK a mixed system rather than a half-finished one. Science, engineering, medicine, schools and shops are metric; roads, pubs and everyday conversation keep some imperial units, which is why the country still uses miles on road signs and many people give their weight in stones.
When did metric units become legal in Britain?
Metric units first became lawful for contracts in 1864 and for all purposes in 1897. Victorian Parliaments debated a full switch several times. A select committee in 1862 favoured adopting the metric system, and the Weights and Measures (Metric System) Act 1897 legalised metric units for trade without making them compulsory.
For the next sixty years the two systems coexisted, with imperial dominant. A Board of Trade review, the Hodgson Committee, recommended compulsory metrication and decimal currency in 1951, but the government of the day did not act on it.
What happened on 24 May 1965?
The government formally backed metrication for the first time. In a written reply to a parliamentary question from John Horner MP, the President of the Board of Trade, Douglas Jay, said British industry should adopt metric units “sector by sector”, with the greater part of the change made within ten years. The move followed a request from the Federation of British Industries, whose members wanted to sell more easily to metric export markets.
Two years earlier, the Weights and Measures Act 1963 had already tied imperial units to metric ones by defining the yard as exactly 0.9144 metres and the pound as exactly 0.45359237 kilograms. Those definitions remain in force today, which is why every imperial-to-metric conversion has an exact answer.
Why did metrication stall in the 1970s?
The programme was voluntary, and political support faded before the consumer-facing stages arrived. A Metrication Board was set up in 1969 to coordinate the change, and many industries did convert: building, engineering and education moved to metric during the late 1960s and 1970s. Decimal currency arrived on 15 February 1971, but that was a separate reform of money, not measurement.
Everyday units proved harder. In December 1970 the government postponed a plan to convert speed limit signs to km/h, and no new date was ever set. The UK joined the European Economic Community in 1973, and European directives on units of measurement, notably Directive 80/181/EEC, began to shape the timetable for trade. In 1980 the Metrication Board was abolished, and the government left further change to be driven by those trade rules rather than a national campaign.
When did shops have to switch to metric?
Packaged goods went metric on 1 October 1995 and loose goods on 1 January 2000. Both deadlines came from the Units of Measurement Regulations 1994, which removed most imperial units from use in trade. After those dates a trader could still show pounds and ounces, but only as a supplementary figure next to the metric one.
| Date | What changed | What shoppers noticed |
|---|---|---|
| 1 October 1995 | Packaged goods must be marked with a metric quantity | Labels such as 454 g (1 lb) became the norm; spirits in pubs settled on 25 ml or 35 ml measures |
| Mid-1990s | Fuel pumps completed the move from gallons to litres | Petrol priced per litre, while car economy stayed in miles per gallon |
| 1 January 2000 | Loose goods sold by weight must be weighed and priced in metric | Market stalls and greengrocers priced fruit, veg and cheese per kg |
| 2009 | EU Directive 2009/3/EC removed the deadline for imperial supplementary indications | Dual labels such as 500 g (1 lb 1.6 oz) could continue indefinitely |
The arithmetic on old dual labels is easy to check: 1 lb is 453.59 g, so a 1 lb pack was labelled 454 g, and 500 g is 17.64 oz, or 1 lb 1.6 oz. If you want to do the same sums yourself, the weight converter handles grams, ounces and pounds.
Who were the Metric Martyrs?
They were market traders prosecuted for selling loose goods in imperial units after the 2000 deadline. The best known was Steve Thoburn, a Sunderland greengrocer convicted in 2001 for using scales that weighed only in pounds and ounces. His appeal, Thoburn v Sunderland City Council, was dismissed by the High Court on 18 February 2002, and the European Court of Human Rights declared a later application inadmissible in 2004.
The case is still cited by lawyers, though not for its weights and measures content. In his judgment Lord Justice Laws described some Acts of Parliament as “constitutional statutes” that cannot be repealed by implication, an idea that has shaped later constitutional cases.
Is the UK still going metric?
The position has been stable for years, and recent governments have chosen to keep it. In 2022 the government consulted on giving traders more freedom to use imperial units. Its response, published on 27 December 2023, reported that 98.7% of respondents wanted metric to remain either the main unit or the only unit, and it made no change to the law beyond issuing new guidance on showing imperial units alongside metric ones.
Two smaller changes followed. From 19 September 2024, still and sparkling wine can be sold in 568 ml “pint” bottles in Great Britain. And the Product Regulation and Metrology Act 2025, which received Royal Assent on 21 July 2025, gives ministers new powers to make rules on units of measurement, while expressly stopping them from restricting the pint for draught beer, cider and milk in returnable containers.
Which imperial units did the UK keep?
The pint for draught beer, cider and returnable milk bottles, the troy ounce for precious metals, and the mile, yard, foot and inch for road signs and speed. Every other imperial unit can still appear in trade, but only as a supplementary indication next to a metric figure. In everyday life, of course, nothing stops anyone measuring a room in feet or weighing themselves in stone.
Frequently asked questions
What year did the UK go metric?
There is no single year. The government backed metrication on 24 May 1965, packaged goods went metric on 1 October 1995 and loose goods on 1 January 2000. Some imperial units, such as the mile and the draught pint, were never converted.
When did the UK stop selling food in pounds and ounces?
Packaged food had to carry a metric quantity from 1 October 1995, and loose food sold by weight had to be weighed and priced in metric from 1 January 2000. Pounds and ounces can still be shown alongside the metric figure.
Did the EU force the UK to go metric?
Not entirely. The UK government chose to start metricating in 1965, before joining the EEC in 1973. European directives later set deadlines for units used in trade, which the UK agreed to and implemented through its own regulations.
Is decimalisation the same as metrication?
No. Decimalisation changed the currency to 100 pence in a pound on 15 February 1971. Metrication is the move to metric units of measurement, which happened gradually between 1965 and 2000.
Has the UK changed its metric rules since Brexit?
Only slightly. A 2022 consultation led to no change in the core rules, and from 19 September 2024 wine may be sold in 568 ml pint bottles. Metric remains the primary legal unit for trade.
Sources
- Choice on units of measurement: consultation response, GOV.UK, December 2023
- Prepacked still and sparkling wine quantities, GOV.UK
- Weights and Measures Act 1985, section 8, legislation.gov.uk
- Product Regulation and Metrology Act 2025, section 5, legislation.gov.uk
- Towards a metric Britain (in fits and starts), Metric Views, UK Metric Association (a pro-metric campaign group)