Weights and measures: Legal requirements and compliance

Goods sold by weight or measure must be sold in metric quantities. For example:

• if you sell by weight, you use kilograms and grams instead of pounds and ounces
• if you sell by volume, you use litres instead of pints, or cubic metres instead of cubic feet
• if you sell by length, you use metres instead of feet and inches

You must mark packaged goods with the metric measure. If you want, you can also show the imperial measure as well. But it must not be more prominent than the metric measure.

There are no restrictions which limit the range of sizes pre-packaged goods (except for wines and spirits) can be packed in. Aerosol products can be packed by weight and volume. Even though goods can now be packed in any size, you can continue to use traditional standard pack sizes if you wish.

Exceptions

There are only a few exceptions to the metric unit rules. The following can be sold by imperial units:

• pints of draught beer and cider
• pints of milk in returnable containers
• troy ounces of precious metals 

Trading Standards

Northern Ireland Trading Standards officers can advise you. They also make occasional checks to make sure you're following the rules. 

There are rules which regulate the way businesses weigh, measure and label packaged goods.

Businesses must comply with the 'Three Packers Rules', which include:

• the average contents of packages should not be less than the nominal quantity
• the proportion of packages that are short of the stated quantity by a defined amount - the tolerable negative error (TNE) - should be less than a specified level
• no package should be short by more than twice the TNE

Businesses must ensure packages meet the three rules - either by using prescribed equipment to make up each package or checking sample packages. Businesses that check each package are not obliged to keep records, but if no records are kept each package must contain at least the stated minimum.

Businesses that check the contents by sampling must use a system that ensures packages meet the three rules. They must keep records of their checks for at least one year from the date the packages leave the premises, or until the date by which the contents must be consumed if indicated.

Approved equipment in Northern Ireland should be marked 'CE' or 'UKNI CE' with a black 'M' on a green background and a four-digit number. A black 'M' with the year of approval on a white background is also allowed. Your equipment supplier should be able to give you more information.

The weight of any package must not include the weight of the packaging. In most circumstances, you must sell by metric weights and measures.

Northern Ireland Trading Standards officers can advise you. They also make occasional checks to ensure you're following the rules. 

All pre-packed goods (with the exception of wines and spirits) can be packaged in any size.

You can package bread in any size. You may use traditional quantities of 400 grams multiples if you wish. Whatever package size you decide to use, it must be clearly displayed on the packaging.

All bread that is sold in quantities weighing over 5 grams and less than 25 kilograms must now be packaged using the average system of quantity control. For example, for a 400 gram loaf this would mean:

• the average loaf must weigh at least 400 grams
• at most one in 40 loaves can weigh less than 388 grams
• no loaf can weigh less than 376 grams

You must also allow for weight loss as loaves dry out. Loaves displayed for sale must meet their weight targets at all times.

For more information on the average system of control, see selling fixed-weight packaged goods.

Responsibility for compliance with the rules rests with the person baking or finishing the baking process, not with the person packaging the goods.

Retailers who wish to have their bread treated under the minimum system rather than the average system must notify their local Trading Standards office. The bread must still be checked to ensure it is at least the weight stated.

Northern Ireland Trading Standards officers can advise you. They also make occasional checks to make sure you're following the rules. 

Unwrapped bread

Unwrapped bread can only be sold when one of the following applies:

• the quantity (weight) of the bread is indicated on a ticket displayed right beside that loaf
• there is a readily available notice listing the forms of unwrapped loaves of bread for sale, including the quantity

There are exemptions. The requirements don't apply to:

• unwrapped loaves in quantities of 400g multiples
• unwrapped loves that weigh 300g or less
• bread supplied to be consumed on the buyer's premises when the contract states each delivery will be over 25kgs altogether and will be weighed upon delivery. 

In general, meat and poultry must be sold by weight.

Most pre-packed items must be marked with their net weight - excluding packaging.

Items that aren't pre-packed can be sold by net weight or gross weight - including packaging. However, there are strict limits on what the packaging can weigh. If you want to sell by gross weight, ask your local Trading Standards office for advice.

You must let the customer know the weight before they pay. This is usually done by weighing the product in front of them. You must use scales that are approved for trade use and stamped to show they have been tested. Ask your equipment supplier for advice about this. Approved equipment should be marked 'CE' or 'UKNI CE' with a black 'M' on a green background and a four-digit number. A black 'M' with the year of approval on a white background is also permitted.

Make sure customers understand if the weight of the product will change. For example, if someone buys some meat but asks for it to be trimmed or boned, causing a weight reduction.

You must display the prices of your products. Pre-packed items must be marked with the price. It must also be easy for the customer to see the unit price - for example, price per kilogram. For items that are not pre-packed, you usually need to display the unit price.

Northern Ireland Trading Standards officers can advise you. They also make occasional checks to make sure you're following the rules and ensure compliance. 

If you sell loose fruit and vegetables, you'll usually sell them by weight. You can choose to sell by:

• net weight - the weight without wrapping or containers
• gross weight - the weight including wrapping

There are limits on the weight of wrapping you can use. Ask the Northern Ireland Trading Standards Service for advice.

However, two groups of produce don't have to be sold by weight, unless you want to do so. They are:

• countable produce that can be sold by number, such as apples, bananas and onions
• some salad products that can be sold by the bunch, such as spring onions and carrots

Pre-packed fruit and vegetables must be sold by net weight - or by number if they're countable products. The pack must be clearly marked with the contents. Pre-packed goods usually have the weight or quantity (ie number) marked on the packet.

In the case of 'countable' produce you don't have to mark the package with the number if the contents are clearly visible to a buyer and the number of products inside is eight or less.

You must let customers know the weight of the produce before they buy it. Usually, loose produce is weighed in front of the customer.

The weighing machine you use must be approved for trade use and stamped to show it's been tested. Ask your equipment supplier for advice on this. Approved equipment should be marked 'CE' or 'UKNI CE' with a black 'M' on a green background and a four-digit number. A black 'M' with the year of approval on a white background is also permitted.

Northern Ireland Trading Standards officers can advise you. They also make occasional checks to make sure you're following the rules and ensure compliance.

You must only sell alcoholic drinks in specified amounts. These are:

• Pints, half pints (or half pint multiples), the rarely used third of a pint and two-thirds of a pint for draught beer, lager and cider
• Multiples of 25 millilitres or 35 millilitres for gin, rum, whisky and vodka except when they're served as part of a cocktail. You must display a notice stating which measure your serve.
• 125 millilitres or 175 millilitres for glasses of wine. You do not need to stick to a specified quantity for servings below 75 millilitres. This allows wine samples or 'tasters' to be sold.

• 250 millilitres for carafes of wine. 

You must use officially stamped measures, metering equipment or glasses. For example, beer can be served using metered pumps or in stamped glasses.

You must make the prices of food and drink clear to intending customers. The easiest way is by clearly displaying a price list. Bars should show the price list at the bar where orders are taken. Restaurants and cafes should show it at the entrance or in the window.

Your prices must include VAT. It must also be made clear if you have a compulsory service charge, a cover charge or a minimum charge.

The Digital Markets, Competition and Consumers Act 2024 (DMCCA) makes it a general requirement not to omit information which the consumer needs to make an informed transactional decision, for example entering a premises or making a purchase.

Northern Ireland Trading Standards officers can advise you. They also make occasional checks to make sure you're following the rules and ensure compliance.

Measures rules for samples for local producers of alcoholic drinks

Local producers may offer sample sizes of the drinks they produce as part of a tour of their production premises, or at an event being held on unlicensed premises to promote food, drink and/or craftwork, or relating to agriculture and which is important to that area of Northern Ireland.

The following samples, allowed per person per day, must not be exceeded:

• 1.5 pints (852mls) beer or cider up to and including 6% ABV
• 1 pint (568mls) beer or cider above 6% ABV
• 3 measures (35mls) of any spirit
• 3 measures (70mls) of any liqueur

The Office for Product Safety and Standards has policy responsibility for the regulation of measuring instruments. It has statutory duty to carry out market surveillance activities. This is to ensure instruments that do not comply with legal and technical requirements are neither placed on the market nor put into use.

Measuring instruments

The UK regulates the following types of measuring instruments, including: 

• water meters
• gas meters
• active electrical energy meters
• fuel dispensers
• road tankers
• automatic catchweighers
• automatic gravimetric filling instruments
• automatic discontinuous totalisers
• automatic rail weighbridges
• beltweighers
• taximeters (responsibility of the Department for Transport)
• material measures of length, capacity serving measures
• exhaust gas analysers (responsibility of the Department for Transport)

Non-automatic weighing instruments

A non-automatic weighing instrument requires an operator to be involved in the weighing process. The Non-Automatic Weighing Instruments Regulations covers a wide range of applications, for example:

• scales used in a greengrocers
• weighbridges
• airport baggage weighers
• baby-weighers

Local weights and measures enforcement

It is the responsibility of the Trading Standards Service of Northern Ireland to ensure that businesses comply with weights and measures legislation. The Office for Product Safety and Standards works closely with them to promote consistency and best practice.

Assessing weights and measurements instruments

All measuring instruments used for trade purposes require a Declaration of Conformity. This legal document confirms that production samples of the design meet all essential regulatory and technical requirements.

Conformity assessment for measuring instruments used in Northern Ireland can be carried out by a UK Approved Body or an EU Notified Body.

Where the conformity assessment has been conducted by a UK Approved Body, a 'UKNI CE' mark will be affixed to the instrument. 

Where the conformity assessment has been conducted by an EU Notified Body, a 'CE' mark will be affixed to the instrument.

Self-verification 

Manufacturers, installers and repairers of weighing and measuring equipment approved by the Office for Product Safety & Standards can test, pass and verify their own work. They can also place their products on the market or return them to the market after a repair.
Approved verifiers are subject to regular audits. They are approved for a limited time and this can be taken away if the approved verifier breaks approval conditions.

Identify an approved verifier.

Manufacturers, installers and repairers who want to apply for approved verification status must provide documentation to prove they have an acceptable quality management system.

Enforcement resources

The Office for Product Safety & Standards carries out projects and produces reports and information to help local weights and measures trading standards departments enforce the legislation in the UK.

The weights and measures bulletins contain guidance for inspectors of weights and measures, approved verifiers and notified bodies on the interpretation of weights and measures legislation.

Stamp identification numbers are given to local weights and measures authorities and approved verifiers so that it is possible to identify which party approved a piece of weighing or measuring equipment. 

EEC stamp numbers are allocated to European weights and measures authorities to identify who has approved a piece of weighing or measuring equipment. They are the European equivalent of national stamp numbers.