Quick answer: Only a handful of imperial units can still be used on their own in UK trade: the pint for draught beer, cider and returnable milk bottles, and the troy ounce for precious metals. Miles, yards, feet and inches remain legal on road signs. Other imperial units may appear in trade only beside a more prominent metric figure.
“Legal” means different things depending on where a unit is used. Shops and other traders are tightly regulated, road signs follow their own rules, and in private life there are no restrictions at all. Sorting units into those three levels is the clearest way to see where imperial measures stand today, and it complements our broader guide to the UK measurement system.
Which imperial units can be used on their own?
Only the pint and the troy ounce, and each only for specific goods. Section 8 of the Weights and Measures Act 1985 lists the units lawful for trade, and these are the only imperial units among them. Both come with conditions:
- The pint (568.26125 ml) for draught beer or cider, and for milk in returnable containers such as doorstep glass bottles. Draught beer must be sold in a third, half or two-thirds of a pint, or multiples of half a pint. Our guide to the size of a pint of beer in ml covers this in detail.
- The troy ounce (31.1034768 g) for transactions in gold, silver and other precious metals. It is about 9.7% heavier than the everyday avoirdupois ounce of 28.35 g, so a price per troy ounce cannot be compared directly with a price per ordinary ounce.
The pint now has extra protection. The Product Regulation and Metrology Act 2025, which gives ministers new powers over units of measurement, says in section 5(4) that those powers cannot be used to prevent or restrict the pint for draught beer, cider or milk in returnable containers.
Are miles, yards, feet and inches legal on road signs?
Yes. Road signs are governed by traffic law, which still uses imperial units for distance and speed. The Traffic Signs Regulations and General Directions 2016 give distances in miles and yards and speed limits in miles per hour. Height and width limits use feet and inches, and since 2016 new signs of that type must also show the limit in metres.
The history of that exemption, and the 1970 decision not to convert speed limits, is covered in why the UK still uses miles.
Which imperial units can be used alongside metric?
Almost all of them, as long as the metric figure is shown and is the more prominent. Part VI of Schedule 1 to the 1985 Act defines a long list of imperial units, from the mile, furlong and chain to the gallon, stone, hundredweight and grain, under a heading that says they “may not be used for trade except as supplementary indications”. The imperial figure must be in characters no larger than the metric one.
| Imperial unit | Exact metric value | Status in UK trade | Where you still see it |
|---|---|---|---|
| Mile | 1,609.344 m | Supplementary only | Road signs, running, rail mileposts |
| Yard | 0.9144 m | Supplementary only | Road signs, fabric shops alongside metres |
| Foot | 0.3048 m | Supplementary only | Height, bridge clearances, property |
| Inch | 25.4 mm | Supplementary only | Screen sizes, tyres, pipe threads |
| Acre | 4,046.86 m² (0.405 ha) | Supplementary only | Land and garden sizes |
| Square foot | 0.0929 m² | Supplementary only | Floor areas in property listings |
| Gallon | 4.54609 L | Supplementary only | Fuel economy in mpg |
| Pint | 568.26 ml | On its own for draught beer, cider and returnable milk; otherwise supplementary | Pubs, doorstep milk, recipes |
| Fluid ounce | 28.41 ml | Supplementary only | Older recipes, baby bottles |
| Pound | 453.59 g | Supplementary only | Dual labels, body weight |
| Ounce | 28.35 g | Supplementary only | Dual labels, recipes |
| Stone | 6.35 kg | Supplementary only | Body weight |
| Hundredweight | 50.80 kg | Supplementary only | Rarely; some farm and coal trade history |
| Troy ounce | 31.10 g | On its own for precious metals only | Gold and silver prices |
So a shop can label cheese “500 g (1 lb 1.6 oz)” or price apples at “£2.50 per kg (£1.13 per lb)”, but cannot price them in pounds alone. The full rules on dual pricing, with examples of lawful and unlawful labels, are in is it legal to sell in pounds and ounces.
Are there any restrictions outside trade?
No. The law controls units used for trade and on official signs, not how people talk, cook or measure at home. You can give your height in feet and inches, weigh yourself in stone, follow a recipe in cups or measure a shed in feet without breaking any rule. Many people do all of these, which is why imperial units feel far more alive in Britain than the trade rules suggest.
A few professional fields also keep imperial or non-metric units by international convention rather than UK law. Aviation, for example, measures altitude in feet and distance in nautical miles across most of the world. Screen sizes and many plumbing fittings are still described in inches because manufacturers use those standards globally. For definitions of every unit mentioned here, see the units of measurement guide.
Which imperial units lost their legal status?
Most imperial units stopped being lawful as primary units for trade under the Units of Measurement Regulations 1994. Packaged goods had to carry metric quantities from 1 October 1995, and loose goods sold by weight had to be weighed and priced in metric from 1 January 2000. Petrol, carpets, timber and greengrocery all made the switch around that time.
A few units were dropped more quietly. The acre, for instance, could once be used for land registration, but that permission ended at the close of 2009, so today it appears only alongside hectares. None of these units is banned from ordinary speech; they simply cannot be the main unit in a sale. The full sequence of dates is set out in when the UK went metric.
Could the rules on imperial units change?
The core rules have just been reviewed and left in place, but the legal framework is being modernised. A 2022 consultation asked whether traders should have more freedom to use imperial units. The government’s response in December 2023 reported that 98.7% of 100,938 responses wanted metric to remain the main or only unit, and no change to the law followed.
The Product Regulation and Metrology Act 2025 will eventually move the list of units out of the 1985 Act and into new metrology regulations. As of October 2026 those provisions are not yet in force, and any new regulations would need to be laid before Parliament. Until then, the position described above is the law.
Frequently asked questions
Is the pint still legal in the UK?
Yes. The pint can be used on its own for draught beer and cider and for milk in returnable containers. For other goods it may appear only alongside a metric quantity.
Can I sell things in feet and inches?
Only as a supplementary indication. A length of timber or fabric must be sold by metric length, but you may show feet and inches alongside, provided the metric figure is the more prominent.
Why can gold be sold in troy ounces?
The troy ounce is the international standard for pricing precious metals, so UK law allows it for transactions in gold, silver and other precious metals. One troy ounce is 31.1034768 g.
Is it illegal to use imperial units in everyday life?
No. The restrictions apply to units used for trade and on official signs. Personal use, conversation, recipes and hobbies can use any units you like.
Are acres still legal in the UK?
Acres can be used freely in conversation and may appear in trade as a supplementary figure next to hectares or square metres. One acre is 4,046.86 square metres, or about 0.405 hectares.
Sources
- Weights and Measures Act 1985, section 8 and Schedule 1, legislation.gov.uk
- Product Regulation and Metrology Act 2025, section 5, legislation.gov.uk
- Choice on units of measurement: guidance on markings and sales, GOV.UK
- The Traffic Signs Regulations and General Directions 2016, legislation.gov.uk
- Units of measurement, Business Companion (Chartered Trading Standards Institute)
- Acres are abolished under EU ruling, Farmers Weekly, July 2008