By Jayson · Updated August 2026 · 10-minute read
UK average weight legislation is the Weights and Measures (Packaged Goods) Regulations 2006, and it governs prepacked goods sold by a stated nominal quantity — not the scale itself. Every batch has to satisfy three rules: the average contents must meet or exceed the nominal quantity, only a small proportion of packages may fall short by more than a tolerance called T1, and no single package may ever fall short by more than T2, which is always exactly twice T1.
Most of our UK compliance guides — UK Weighing Scale Regulations, Legal-for-Trade Scales in the UK — cover the instrument: is the scale itself accurate and approved. UK average weight legislation is a different, complementary question: given an accurate scale, is what actually goes into the pack close enough to what the label claims? Both matter, and a business can have a perfectly compliant scale while still failing average weight legislation if its filling process runs consistently light.
This guide covers what UK average weight legislation actually requires, the three packers' rules in plain English, the official Tolerable Negative Error table, worked examples showing exactly how to calculate T1 and T2 for a real product, a free calculator, and who enforces all of this.
In this guide
- What UK average weight legislation actually is
- The three packers' rules, in plain English
- T1, T2, and the official TNE table
- How to calculate T1 and T2: worked examples
- Three packers' rules calculator
- The e-mark: what it means and whether to use it
- Who enforces UK average weight legislation
- Verify this yourself: official sources
- Common mistakes
- FAQ
What UK Average Weight Legislation Actually Is
UK average weight legislation is the Weights and Measures (Packaged Goods) Regulations 2006 (SI 2006/659), made under the Weights and Measures Act 1985. The 2006 Regulations implement what was originally EU Directive 76/211/EEC, and they've been retained in UK law after Brexit — the underlying rules and the official tolerance table haven't changed.
The Regulations apply to prepacked goods made up in a constant nominal quantity — a bag of flour marked 1kg, a jar of coffee marked 200g, a bottle of shampoo marked 500ml — across a scope of 5g/5ml up to 10kg/10L (with the table extending further for larger quantities). The legal duty sits with the packer or importer: it's their responsibility to ensure every batch of packages satisfies the three rules covered below, not the retailer selling the finished product.
This is a genuinely different compliance question from the one covered in our other UK guides. UK weighing scale regulations ask whether the instrument is accurate and legally approved. UK average weight legislation asks whether the filling process — using that instrument — actually delivers what the label promises, checked statistically across a whole batch rather than instrument by instrument.
That distinction matters in practice more than it might sound like it should. A business can own a scale with a perfectly current M mark, correctly verified and never tampered with, and still fail an inspection under UK average weight legislation — because the accuracy of the scale only tells you the reading is trustworthy at the moment of weighing, not whether the filling line consistently aims high enough above the nominal quantity to survive normal process variation. A filling process that runs exactly on target, with no margin at all, will inevitably produce some packages below nominal simply through ordinary variation — which is precisely why the three rules exist as a statistical system rather than a single "must never read under nominal" requirement.
The Three Packers' Rules, in Plain English
Regulation 4(1) of the 2006 Regulations sets out three rules a packer must satisfy. In the legislation's own language:
- Rule 1 — the contents of the packages shall be not less on average than the nominal quantity.
- Rule 2 — the proportion of packages with a negative error greater than the tolerable negative error shall be sufficiently small to satisfy the statistical batch test in Schedule 2.
- Rule 3 — no package shall have a negative error greater than twice the tolerable negative error.
In plainer terms:
- Rule 1 (the average rule) — across the whole batch, packages can't systematically run light. Some can be a touch over, some a touch under, but the average has to be at or above the stated nominal quantity.
- Rule 2 (the T1 rule) — a small number of individual packages are allowed to fall short by more than the tolerance (called T1), but only up to a statistically limited proportion of the batch — not an unlimited number.
- Rule 3 (the T2 rule) — this is the hard floor. No single package, ever, may fall short by more than twice T1 (called T2). A pack that fails this is classed as "inadequate" and it's an absolute breach on its own, independent of how the rest of the batch performs.
T1, T2, and the Official TNE Table
T1 is shorthand for the Tolerable Negative Error (TNE) — the maximum a package is allowed to fall short of its nominal quantity before it counts as "non-standard" under Rule 2. T2 is always exactly twice T1 — the absolute floor under Rule 3.
The TNE table is set out in Schedule 3 of the 2006 Regulations, and it alternates between a percentage of nominal quantity and a fixed gram/millilitre value depending on the size band:
| Nominal quantity | TNE (T1) |
|---|---|
| 5g–50g | 9% of nominal quantity |
| 50g–100g | 4.5g |
| 100g–200g | 4.5% of nominal quantity |
| 200g–300g | 9g |
| 300g–500g | 3% of nominal quantity |
| 500g–1,000g | 15g |
| 1,000g–10,000g | 1.5% of nominal quantity |
| 10,000g–15,000g | 150g |
| Above 15,000g | 1% of nominal quantity |
Where T1 is calculated as a percentage, the result must be rounded up to the nearest 0.1g or 0.1ml — never rounded down, since that would let a batch pass on a technicality it hasn't actually earned.
Notice that each band's value lines up exactly with the next at the boundary — at 100g, the 9% band above gives 4.5g, matching the fixed 4.5g value the next band starts with. That continuity is intentional: it's how you can tell a TNE table is built correctly rather than transcribed with a row out of place, which is exactly the kind of error worth double-checking against the official legislation text rather than a secondary source.
How to Calculate T1 and T2: Worked Examples
Calculating T1 and T2 correctly for your product's nominal quantity is the first step before any batch testing can begin.
Here's exactly how the calculation works, with three real examples across different bands.
Example 1 — a 750g bag of pasta (fixed-value band): 750g falls in the 500g–1,000g band, where T1 is a fixed 15g. No percentage calculation needed. T1 = 15g, T2 = 30g. A single pack below 720g (750g − 30g) would fail Rule 3 outright.
Example 2 — a 150g jar of spread (percentage band): 150g falls in the 100g–200g band, where T1 is 4.5% of nominal quantity. 4.5% of 150g = 6.75g, rounded up to the nearest 0.1g = 6.8g. T1 = 6.8g, T2 = 13.6g. A single pack below 136.4g would fail Rule 3.
Example 3 — a 2,500g bag of dog food (percentage band, larger quantity): 2,500g falls in the 1,000g–10,000g band, where T1 is 1.5% of nominal quantity. 1.5% of 2,500g = 37.5g, which is already an exact multiple of 0.1g so no rounding adjustment changes it. T1 = 37.5g, T2 = 75g. A single pack below 2,425g would fail Rule 3.
The pattern is always the same: find the right band, apply that band's percentage or fixed value to get T1 (rounding percentage results up to 0.1g/ml), then double it for T2.
Three Packers' Rules Calculator
Enter your product's nominal quantity to get its T1 and T2 automatically, using the official Schedule 3 table above.
This calculator applies the official Schedule 3 rounding rule automatically. It's a planning tool, not a substitute for your own batch reference testing under Schedule 2.
The e-mark: What It Means and Whether to Use It
The e-mark — a lowercase "e" printed near the nominal quantity on a package — is a voluntary symbol under UK average weight legislation. When it's used, it's a formal declaration that the packages comply with the average quantity system in the 2006 Regulations, and it remains recognised in UK law post-Brexit.
The e-mark isn't required — a business can be fully compliant with the three packers' rules without ever printing it. What the e-mark actually signals is that the packer's own quality system includes the full reference-test compliance process, not just an informal claim of compliance. Businesses that trade internationally sometimes use it because it's a mark accreditation bodies and overseas partners recognise; businesses that only sell domestically often skip it since it adds a labelling commitment without a corresponding legal requirement to have one at all.
Who Enforces UK Average Weight Legislation
Local authority Trading Standards, acting in their capacity as weights and measures authorities, enforce the Packaged Goods Regulations 2006 — the same bodies that enforce UK weighing scale regulations, but a genuinely separate role.
In practice, enforcement means batch sampling and reference testing under Schedule 2 of the Regulations: inspectors take a sample from a production batch, weigh each package, and check the results against all three rules — the batch average, the proportion exceeding T1, and whether any single pack exceeds T2. This is a statistical test on a real batch, not a single spot-check of one package, which is why the rules are written the way they are — Rule 1 and Rule 2 only make sense measured across a batch, while Rule 3 applies to every individual pack.
Businesses subject to this legislation are expected to keep their own production and checking records, since Trading Standards can request them as part of an inspection rather than relying solely on their own sampling. In practice, this means a business that takes UK average weight legislation seriously will already be running its own internal batch checks against the same T1/T2 figures an inspector would use, well before any external sampling ever happens — treating the official reference test as a final confirmation of an already-compliant process, not the first time anyone actually checked.
Verify This Yourself: Official Sources
Regulations and official guidance can change, and this guide reflects research current as of August 2026. Before relying on UK average weight legislation for a compliance decision, check directly with:
- legislation.gov.uk — The Weights and Measures (Packaged Goods) Regulations 2006 — the full legal text, including Regulation 4 and Schedules 2 and 3.
- GOV.UK — Packaged goods: weights and measures — official government guidance on the average quantity system.
- Business Companion — Packaged goods: average quantity — the UK's official business-facing guidance service.
See our site disclaimer for how we handle regulatory and standards content generally.
Common Mistakes
- Confusing average weight legislation with scale accuracy rules. A perfectly legal-for-trade scale doesn't automatically mean a filling process complies with the three packers' rules — they're separate compliance questions.
- Rounding a percentage-based T1 down instead of up. The rounding rule specifically requires rounding up to the nearest 0.1g/ml — rounding down understates the tolerance and could mask a genuine Rule 3 breach.
- Treating T1 as the only limit that matters. Rule 3's absolute T2 floor applies to every single package, regardless of how well the batch performs on Rules 1 and 2.
- Assuming the e-mark is mandatory. It's entirely voluntary — plenty of fully compliant UK packages never carry it.
- Testing only one or two packages and assuming that represents the batch. Rules 1 and 2 are explicitly statistical, batch-level tests under Schedule 2, not single-sample checks.
- Forgetting that the packer or importer carries the legal duty, not the retailer. A shop selling a non-compliant pack usually isn't who's actually liable for the shortfall.
Frequently Asked Questions
What is UK average weight legislation? The Weights and Measures (Packaged Goods) Regulations 2006, made under the Weights and Measures Act 1985. It requires prepacked goods sold by nominal quantity to satisfy the three packers' rules, so customers aren't systematically short-changed.
What are the three packers' rules? Rule 1: batch average must meet the nominal quantity. Rule 2: only a small proportion of packages may exceed T1. Rule 3: no single package may exceed T2, which is always twice T1.
How do I calculate T1 and T2 for my product? Find your nominal quantity's band in the official TNE table, apply that band's percentage or fixed value to get T1 (rounding percentage results up to 0.1g/ml), then double it for T2.
What is the e-mark and do I need it? A voluntary symbol declaring compliance with the average quantity system. It's not mandatory, but using it means committing to the full reference-test compliance process, not just an informal claim.
Who enforces UK average weight legislation? Local authority Trading Standards, as weights and measures authorities, through batch sampling and reference testing — separate from their enforcement of weighing instrument accuracy.
What happens if a package fails Rule 3? A single package with a negative error greater than T2 is classed as inadequate and is an absolute breach on its own, regardless of how the rest of the batch performs.
More Scale Calibration Guides
- UK Weighing Scale Regulations — scalecalibration.net/uk-weighing-scale-regulations/ — the instrument-accuracy side of UK compliance.
- Legal-for-Trade Scales in the UK — scalecalibration.net/legal-for-trade-scales-uk/ — which businesses need trade-approved equipment.
- Scale Calibration Services — scalecalibration.net/scale-calibration-services/ — keeping your filling-line scales accurate.
- Calibration Weights: Which Class & Size — scalecalibration.net/calibration-weights/ — certified weights for checking any scale.
- Best Scales — scalecalibration.net/category/best-scales/ — buying guides across scale types.
