Weights and measures law makes sure customers get the quantity they pay for. It applies when you sell loose goods by weight or volume, when you pack goods before sale and when you import packaged goods. Your council's trading standards service, the local weights and measures authority, enforces it and can test your equipment and your packages.
Use metric units
You must use metric units, such as grams, kilograms, millilitres and litres, when you sell packaged or loose goods. You can show an imperial quantity alongside, but it cannot stand out more than the metric one.
Only three products can be sold in imperial units: draught beer or cider by the pint, milk in returnable containers by the pint, and precious metals by the troy ounce.
Sell some goods only in fixed quantities
Some goods must be sold in set quantities, called specified quantities.
Alcohol sold by the glass
The quantities you can use when you sell alcohol by the glass.
| Drink | Quantities you can sell |
|---|---|
| Still wine | 125ml, 175ml, and multiples of 125ml and 175ml |
| Port, sherry or other fortified wine | 50ml, 70ml, and multiples of 50ml or 70ml |
| Gin, rum, vodka and whisky | 25ml and multiples of 25ml, or 35ml and multiples of 35ml, but not both on the same premises |
| Draught beer and cider | A third, a half or two-thirds of a pint, and multiples of half a pint |
Still wine, sparkling wine, fortified wine and spirits sold in bottles or similar containers must also be in specified quantities within a minimum and maximum volume. There are no specified quantities for packaged beer or cider. Solid fuel sold loose can only be sold in 25kg, 50kg or multiples of 50kg.
Use equipment that is passed for trade use
Weighing or measuring equipment of a prescribed type that you use for trade must have been passed by an inspector or approved verifier as fit for that use, and must carry a stamp showing it has been passed. Using equipment that has not been passed is an offence, and the equipment can be forfeited. You cannot use domestic scales to weigh goods you sell.
Pack goods to the right quantity
The packaged goods rules cover products that are sold sealed, contain between 5g and 25kg or 5ml and 25 litres, and are packed in the same nominal quantity as other products of the same type. You can pack them in one of two ways.
Under the minimum system, every package contains at least the quantity on the label. It can contain more, but never less.
Under the average system, you pack to an average quantity shown on the label. You must check random samples to make sure they meet the three packers' rules:
- The contents of the packages must not be less, on average, than the quantity on the label.
- Only a small number of packages can fall below a set margin of error, known as the tolerable negative error.
- No package can be short by more than twice the tolerable negative error.
Tolerable negative error
The margin of error for each nominal quantity under the average system.
| Nominal quantity (g or ml) | Tolerable negative error |
|---|---|
| 5 to 50 | 9% of the quantity |
| 50 to 100 | 4.5g or ml |
| 100 to 200 | 4.5% of the quantity |
| 200 to 300 | 9g or ml |
| 300 to 500 | 3% of the quantity |
| 500 to 1,000 | 15g or ml |
| 1,000 to 10,000 | 1.5% of the quantity |
| 10,000 to 15,000 | 150g or ml |
| More than 15,000 | 1% of the quantity |
When you work out the error as a percentage, round the weight or volume up to the nearest 0.1 of a gram or millilitre. Your local trading standards service can help you set up checks for the average system.
Label the quantity
Mark the nominal quantity on every package in metric units. The marking must be permanent and easy to see, and the figures must be at least the minimum height for the quantity.
Minimum height of the quantity marking
The smallest figures you can use to mark the nominal quantity.
| Nominal quantity | Minimum height |
|---|---|
| Not more than 50g or 5cl | 2mm |
| More than 50g or 5cl, up to 200g or 20cl | 3mm |
| More than 200g or 20cl, up to 1kg or 1 litre | 4mm |
| More than 1kg or 1 litre | 6mm |
Keep records of your checks
If you pack to the average system, you must record the results of your sample checks and show that they meet the three packers' rules. Keep the records for one year after the packages leave you, or until the date marked on the package by which the product should be eaten, if that comes first. You do not need records if you use the minimum system or weigh or measure every package.
Penalties
Failing to pack, mark or keep records as the packaged goods rules require is an offence, with a fine up to level 5 on the standard scale. Knowingly making a false record, or altering a record to deceive, can also lead to up to three months in prison.
Legal basis
Primary legislation and key regulations
Browse UK legislation (opens in a new tab) legislation.gov.uk