LABELLING & REGULATORY · LEGAL METROLOGY

Net Quantity, Average Weight and Legal Metrology on South African Food Labels

By Mthokozisi Nkosi, Food Safety Specialist & Lead Auditor, ASC Food Safety · 15 min read

Net quantity on a South African food label is governed twice over. The Legal Metrology Act 9 of 2014, administered by the NRCS, controls the declaration and the actual contents of a prepackage, with SANS 289:2022 incorporated under it by Notice 877 in Government Gazette 41854 of 24 August 2018, as amended. Regulation 9 of R146 of 2010 separately requires net contents in SI units. Short measure is an offence.

Who regulates net quantity on a South African food label?

The National Regulator for Compulsory Specifications administers the Legal Metrology Act 9 of 2014, which replaced the Trade Metrology Act 77 of 1973. The NRCS controls how a quantity is declared on a prepackage and whether the pack actually contains it. Regulation 9 of R146 of 2010 separately makes net contents in SI units a mandatory particular enforced by environmental health practitioners. One figure, two regulators.

This is the part most technical managers get wrong. When your local environmental health practitioner inspects against R638 of 2018 and R146 of 2010, net contents is on the checklist because regulation 9 puts it there alongside the product name, the manufacturer name and address, instructions for use, the ingredient list in descending order and the storage conditions. They check that a figure and an SI unit are present. They will usually not weigh anything.

The NRCS is a different visit with different questions. A legal metrology inspector is interested in whether the declaration complies with SANS 289, whether your filling process delivers the declared quantity, and whether the instruments you rely on to prove that are verified. They will weigh things. The two visits arrive from different departments, on different mandates, and neither one accepts the other’s clearance as evidence.

Sitting behind both is the Consumer Protection Act 68 of 2008. Section 24 deals with product labelling and trade descriptions and section 41 with false, misleading or deceptive representations. A pack that says 500 g and holds 470 g is a misrepresentation as well as a metrology offence, and a competitor or a consumer body can act on it without waiting for an inspector. Our guide to South African food legislation sets out how these Acts overlap.

What does SANS 289 actually control?

SANS 289:2022 is titled “Labelling requirements for prepackaged products (prepackages) and general requirements for the sale of goods subject to legal metrology control”. It is incorporated under the Legal Metrology Act 9 of 2014 by Notice 877 in Government Gazette 41854 of 24 August 2018, as amended. It sets permitted units, how a quantity is written, where it sits on the pack, its prominence and its minimum character heights.

Two things follow from the words “as amended”. The first is that the standard is not static: SABS revises it and the incorporating notice is amended, so check which edition is in force before you rely on an old artwork brief. If your artwork was signed off against an older edition and has not been looked at since, you are compliant with a document that no longer exists. The second is that this is compulsory, not voluntary. People hear “SANS” and file it with the good practice standards. SANS 289 reached you through a Government Gazette notice under an Act of Parliament, which puts it in the same enforcement class as a regulation.

Your fill can be perfect and your label still illegal. Metrology enforcement looks at both, and the label is the cheaper one to get wrong.

The scope reaches wider than food. Anything sold prepackaged by mass, volume, length, area or count and subject to legal metrology control falls inside it, which is why the same standard governs the flour on a supermarket shelf and the paint in the hardware aisle. That matters for food manufacturers because the quantity rules come from metrology rather than from the health regulations, so food specific guidance on labelling is usually incomplete on this point.

How must the net quantity be expressed, and where must it appear?

Under SANS 289 the declaration states the nominal quantity in an SI unit appropriate to the product, in the principal display panel, legible and unobscured by seams, folds, seals or the closure. It must not be qualified by words such as approximately or when packed unless the applicable standard allows it. The permitted forms are plain: the figure and unit alone, or the figure and unit with net, net mass or net contents.

The writing conventions catch more sites than the placement rules do, because they look like typography and they are actually law. A single space separates the number from the unit symbol. No full stop follows a unit symbol, because it is a symbol and not an abbreviation. No letter s is added to make a symbol plural. The k in kg is lower case, since a capital K is the kelvin. The word is net, not nett, which is an old commercial spelling with no standing in a metrology document. And the quantity being declared is mass, not weight, so net mass is right and net weight is a habit imported from American packaging.

Volume declarations follow the same logic. Liquids are declared by volume in millilitres or litres, solids by mass in grams or kilograms, and the decision is not yours to make freely: it follows the product and, for some categories, the applicable product regulation. A viscous product sold by mass in one market and by volume in another is a classic import problem, and our article on importing food into South Africa deals with the wider set of changes an imported label needs.

How big must the net quantity characters be?

SANS 289 prescribes minimum heights for the figures and letters of the quantity declaration, scaled in bands so a 50 g sachet and a 5 kg bag do not carry the same digit size. Confirm from the current published edition whether the height is measured on the numeral or on the capital letters. Because the bands are revised with the standard, confirm the millimetre figure for your pack size against the current published edition, not from an old artwork brief.

I am deliberately not printing a table of heights here. Character height bands are the most commonly misquoted figures in South African labelling, and the numbers circulating in artwork briefs are frequently lifted from European rules or from a superseded edition. If the height on your artwork came from a designer who “knows the standard”, treat it as unverified. The correct source is the published standard, or a reviewer who has it open.

It is worth seeing what a prescribed character height looks like when it is written into South African law, because food regulations do it elsewhere and the drafting is instructive. The Regulations Relating to Soft Drinks, R.1769 of 9 August 1985, as amended by Notice R.317 of 17 April 2012 in Government Gazette 35265, require that where a soft drink contains more than 150 mg of caffeine per litre the main panel carries “High caffeine content” in letters at least 3,0 mm high, and the label carries “Not recommended for children under 12 years of age; pregnant or lactating women; persons sensitive to caffeine” in letters at least 1,3 mm high. Those figures are exact, they are enforceable, and they are measured on the printed pack.

Height alone does not deliver prominence. A declaration printed at the correct height in a pale tint on a busy photographic background is not legible, and legibility is the point of the requirement. Check contrast, check that the figure is not split by a fold or a seam, and check that shrink sleeve distortion has not compressed the numerals below the minimum on the finished pack rather than on the flat artwork. That last one is caught only by measuring a real pack.

What is the average quantity system, and what is a tolerable negative error?

The average quantity system accepts that filling varies and controls the lot rather than the pack. It rests on three rules: the mean contents of the lot must be at least the nominal quantity, only a small defined proportion of packs may fall short by more than the tolerable negative error, and none may fall short by more than twice it. SANS 1841 covers quantity control of prepackage contents.

The tolerable negative error, written TNE and often called T, is the allowance for a single package. It is not a licence to underfill. It exists because no filling head is perfect and because insisting that every single pack meet nominal would force enormous over-fill on every producer in the country. In the international model that the system derives from, published by the International Organisation of Legal Metrology as OIML R87, T is expressed as a percentage of the nominal quantity in some size bands and as a fixed absolute value in others, and the percentage tapers as packs get bigger. Confirm the value that applies to your nominal quantity against the current published standard, or ask us to confirm it for you. Do not copy it from a checkweigher supplier’s brochure written for another jurisdiction.

Two categories of deficient pack matter. A package short by more than T is commonly called a T1 non standard package, and the rules permit only a small proportion of these in a lot. A package short by more than 2T is a T2 package, and the rules permit none at all. That asymmetry is the heart of the system: a lot can carry a handful of slightly light packs and still pass, but a single badly light pack fails it outright.

The proportion of T1 packages a lot may carry, and the sample size used to judge it, come from the sampling plan in the applicable standard and scale with the size of the lot. I am not going to publish a specific plan here for the same reason I did not publish a character height table: the figures are edition dependent and a wrong number costs you more than a missing one. What matters for design purposes is the shape of the rules, and the shape is enough to set up your line correctly.

What is the difference between nominal quantity and actual fill?

SANS 1841 covers quantity control of prepackage contents, and it turns on the gap between the nominal quantity printed on the pack and the actual fill in the pack in front of you. Under the average quantity system the two are never expected to match. Nominal is a promise about the lot, delivered by a distribution whose mean sits at or above the declared figure.

The gap between the two is where your money is. Every gram above nominal is product you gave away, and give away is a direct function of two settings: how high you place the target and how wide your process variation is. Most South African sites I visit control the first and ignore the second. They discovered years ago that setting the target well above nominal stops the complaints, and nobody has looked at the standard deviation since.

Reducing variation is the lever with the return on it. Halving the standard deviation lets you drop the target by roughly the same amount you removed from the spread, on every pack, on every run, for as long as the process holds. Raising the target buys safety at full price. Cutting variation buys the same safety and hands the difference back. The worked example below puts a number on that.

Worked example: a 500 g pack, twenty samples and the target fill

A snack line runs a 500 g nominal pack declared under SANS 289. Twenty consecutive packs from one lot are weighed individually on a verified scale. The masses in grams are 504, 497, 511, 502, 495, 508, 500, 499, 513, 506, 491, 503, 507, 498, 505, 500, 512, 496, 509 and 501. The mean is 502,85 g and the sample standard deviation is 6,04 g.

Take the three rules in order. Rule one asks whether the lot mean is at least nominal. It is: 502,85 g against a nominal of 500 g, a margin of 2,85 g. The standard error of that mean is 6,04 divided by the square root of 20, which is 1,35 g, so the sample mean sits 2,11 standard errors above nominal. The formal test compares the sample mean against nominal less a correction factor times that standard error, and a margin of two standard errors is comfortable. Rule one passes.

Rules two and three depend on T, and T depends on the nominal quantity and the edition of the standard. Rather than guess it, list the deficiencies. Six of the twenty packs fall below nominal: 499 g is 1 g short, 498 g is 2 g, 497 g is 3 g, 496 g is 4 g, 495 g is 5 g and 491 g is 9 g. Every other pack is at or above nominal. Now the result can be read off for any value of T you substitute.

Read it this way. If the applicable T for a 500 g nominal is 9 g or more, this lot passes all three rules with room to spare. If T is smaller, one pack becomes non standard and whether the lot passes depends on the permitted proportion in the sampling plan. If T drops below 4,5 g, the 491 g pack becomes a T2 package and the lot fails outright regardless of how good the mean is. That single pack, nine grams light, is the whole risk in the lot, and no amount of averaging rescues it.

Now the commercial half. The current setting delivers a mean of 502,85 g with a standard deviation of 6,04 g, which means roughly a third of packs sit below nominal. Six of the twenty did. That is legal on the mean and uncomfortable on rules two and three. Two ways to fix it.

• Option A, raise the target. Set the target at nominal plus two standard deviations: 500 + 2 × 6,04 = 512,1 g. Give away becomes 12,1 g per pack, or 2,4 per cent of nominal.
• Option B, cut the variation. Service the filler, stabilise the product density, fix the feed and bring the standard deviation to 3,0 g, then set the target at 500 + 2 × 3,0 = 506,0 g. Give away becomes 6,0 g per pack, or 1,2 per cent.
• The difference between the two options is 6,1 g on every pack for the same statistical safety.
• On a run of 200 000 packs that is 1 220 000 g, which is 1 220 kg, or the equivalent of 2 440 finished 500 g packs of product handed out for nothing.

That is the argument for a checkweigher and a real sampling plan, made in the only language a finance director reads. The compliance benefit is the mean and the tolerance rules. The payback is the variation.

How do you set up a checkweigher and a sampling plan that keeps you legal?

Set the checkweigher from your own measured process variation, not from the tolerance, because the Legal Metrology Act 9 of 2014 tests the contents of the lot. Establish the standard deviation of the filling process for that product and pack format, place the target at nominal plus a multiple of it, set the reject limit against the tolerance, verify the instrument, and record individual masses.

1. Establish the baseline firstWeigh 50 to 100 consecutive packs off a stable run, on a verified scale, before touching a setting. Calculate the mean and the standard deviation for that product on that line. Every setting that follows comes from those two numbers, and they differ by product, by pack format and often by line.
2. Confirm the tolerance that appliesTake the tolerable negative error for your nominal quantity from the current published standard and write the source and edition into the quality plan. A tolerance with no citation is the first thing an inspector questions.
3. Set the target above nominal by a multiple of sigmaTwo standard deviations above nominal is a common working setting, three where the process drifts or where a customer specification imposes a minimum system. Record which multiple you chose and why, because that is a control decision and must be reviewable.
4. Set the reject limit from the tolerance, not the targetThe reject line exists to catch the packs that would breach T and 2T, so it belongs just above nominal less T. Setting it at the target turns the checkweigher into a give away machine that rejects perfectly legal packs.
5. Use the checkweigher to correct the filler, not just to sortFeedback control that trims the filler when the running mean drifts is what holds the standard deviation down. A checkweigher that only pushes light packs off the belt is an expensive sorter that hides the problem.
6. Verify the instrument and keep the certificateAn instrument used to determine quantity for trade must be verified and in date. An unverified scale means your fill records prove nothing, even where the fills themselves were correct.
7. Sample by time and by eventFixed interval sampling through the run, plus a sample at start up, after every changeover, after any filler adjustment, after a stoppage and at the end of the lot. Drift shows up at the events, not in the middle of a steady run.
8. Record individual masses and trend themIndividual values, dated, timed and identified by line, product and lot. A sheet showing only “average OK” is not evidence. The trend of the mean and the standard deviation over weeks tells you a filling head is wearing out before it costs you a lot.

The checkweigher itself is a piece of production equipment with a maintenance, calibration and suitability profile like any other, and certification schemes expect it to be assessed as such. The Equipment Suitability and Maintenance Risk Assessment Template (RA10) at R690 gives you the register, the procedure, the completion guide and a read me in editable Word and Excel, mapped to BRCGS, IFS and SQF clauses, so the checkweigher, the filler and the scales sit on one scored register rather than in three unrelated files.

How is drained mass declared for products in a liquid medium?

Where a solid food is packed in a liquid that is not normally eaten, such as brine, syrup or oil in canned fruit, vegetables or fish, the buyer is buying the solid, so its drained mass is declared in addition to the net contents that regulation 9 of R146 of 2010 requires. The sieve, the drain time and the conditions come from the applicable product standard or NRCS compulsory specification.

The mechanism is straightforward and the detail is where the arguments happen. The contents are emptied onto a sieve of a specified mesh, allowed to drain for a specified time at a specified inclination and temperature, and the retained solid is weighed. Change the mesh, the time or the temperature and the answer changes. The method is prescribed rather than left to the laboratory. Take the method from the standard that governs your product and cite it in your specification.

For several South African food categories that standard is an NRCS compulsory specification rather than a SANS standard alone. Canned fish, canned marine molluscs and canned crustaceans fall under VC 8014. Canned meat products fall under VC 8019. Processed meat products fall under VC 9100. Frozen fish and frozen marine molluscs fall under VC 8017, and smoked snoek under VC 8021. Those specifications carry compositional and labelling requirements alongside the quantity provisions, and they are enforced by the same regulator that enforces the metrology.

Two related traps. The first is a pack that declares only drained mass where both figures are required, which reads as a smaller pack than it is and confuses the shelf comparison. The second is a pack that declares net contents alone on a product where the liquid is clearly not consumed, which overstates what the buyer receives. Both are label problems rather than filling problems, and both are found on a desk review long before a pallet ships. Our summary of the most common food labelling mistakes covers the wider set.

What records does a legal metrology inspector ask for?

A legal metrology inspector, working under the Legal Metrology Act 9 of 2014, wants evidence that you knew the quantity was right when you sold it: fill records for the lot in front of them, verification certificates for the instruments that produced those records, the quality plan setting target and sampling frequency, the source of the tolerance applied, and what you did when the process drifted.

• Individual pack masses by lot, line, product and shift, dated and timed, with the operator identified
• Valid verification certificates for every weighing instrument used to determine quantity for trade, including the checkweigher and the reference scale
• Calibration checks between verifications, with the test mass used and the result recorded
• The written quality plan stating nominal quantity, target fill, control limits, reject limits, sample size and sampling frequency for each product
• A citation for the tolerance applied, naming the standard and the edition it came from
• Out of specification records: what was found, which lot was affected, what was done with it, who authorised the release or the hold
• Filler maintenance and adjustment records, so a step change in the mean can be tied to an event
• Artwork approval records showing who checked the quantity declaration against SANS 289 and when
• For products in a liquid medium, drained mass results with the method and the specification cited
• Traceability from the sampled pack back to the lot, the run and the raw material, and forward to every customer who received it

The last item is the one that decides how expensive a bad day becomes. If an inspector finds a short measure pack and you can identify the lot, the run window and the customers in an hour, the problem is bounded. If you cannot, the problem is every pack of that product in the trade. The Traceability, Withdrawal and Recall Risk Assessment Template (RA20) at R690 scores exactly that capability, and it is the pack to reach for if your last mock recall took longer than four hours.

What happens on a legal metrology inspection or a consumer complaint?

A legal metrology inspection under the Legal Metrology Act 9 of 2014 usually starts without notice, at the factory or at retail. The inspector selects packs from a lot, weighs them on a verified instrument, and compares the result against the declared nominal quantity using the applicable sampling plan. A failed lot brings a written finding, a request for fill and calibration records, and a restriction on the stock.

The complaint route runs the other way and is more common than most manufacturers realise. A consumer weighs a pack at home, finds it light, and complains to the retailer, to the NRCS or on social media. The retailer’s technical team then asks you for the fill data for that lot, that week. Sites that trend their data answer in a morning. Sites that file weight sheets in a lever arch folder spend three days reconstructing something that convinces nobody. Legal metrology is only one of the mandates the NRCS carries into a food factory, and our guide to NRCS compulsory specifications for food covers the product side, the VC numbers and the regulatory file that sits behind them.

What determines the outcome in both routes is the same short list: whether the declaration on the pack complies, whether the lot meets the three rules, whether your instruments were verified, and whether your records were made at the time rather than assembled afterwards. Nothing about that list is unusual. It is the same evidence discipline a BRCGS or FSSC auditor applies to any control point, applied to quantity. Our guide to food hygiene audits covers the general habit, and the training site publishes a longer read on the food safety records every South African food business must keep.

One point on tone. Legal metrology inspectors are technically minded and they respond well to a site that produces its quality plan, its verification certificates and its trended data without being asked twice. The sites that struggle are the ones that argue about the sampling plan before producing a single record. Have the file ready, hand it over, and deal with the finding on its merits.

The net quantity mistakes we find most often on artwork

Most quantity findings are not filling failures but typography, unit choice and placement errors measured against SANS 289 and regulation 9 of R146 of 2010, and they survive three rounds of artwork approval because everybody is looking at the ingredient list and the nutrition table. The declaration is a small piece of text that nobody owns, and it fails in the same eight or nine ways across every category we review.

• Nett instead of net, carried over from an old design or a supplier’s template
• Net weight instead of net mass on a product declared by mass
• A full stop after the unit symbol, or a plural s, so 500 g. or 500 gs
• A capital K in Kg, which is the kelvin and not the kilogram
• No space between the figure and the unit, so 500g rather than 500 g
• An awkward unit that inflates the figure, such as 750 000 mg or 0,75 kg where 750 g is the sensible declaration
• The word approximately, about or minimum in front of the figure, or when packed after it
• The declaration placed on a side panel or a back panel rather than the principal display panel
• The declaration falling across a fold, a seam or under the closure on the finished pack
• Drained mass omitted on a product packed in a liquid medium that is not consumed
• Multipack declarations that state the total but not the number and size of the individual units
• Two different quantity figures on the same pack, one on the front and an old one on the back

None of those cost anything to fix at artwork stage and all of them cost a print run to fix afterwards. This is exactly the work the labelling and regulatory service exists for. We read the artwork clause by clause against R146 of 2010 and SANS 289, mark it up, and hand back a report your designer and your printer can both work from. Standard turnaround is five to seven business days, with a 48 hour express option when the print slot will not move. If claims, nutrition or date marking sit on the same pack, our articles on health and nutrition claims and on best before and use by date marking deal with those panels.

If you would rather build the capability in house so the first pass never leaves the building, the training site runs Essentials of Food Labelling Claims at R1,250 and the fuller Labelling Claims and Regulatory Framework at R1,750, and publishes a detailed guide to South African food labelling regulations under R146.

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Published by ASC Food Safety, South African food safety and quality consultants. This article is general guidance and not a substitute for certification-specific advice.