If your packs are labelled with a weight, Trading Standards can turn up and check them — and "average weight" law is one of the most misunderstood rules in food manufacturing. The good news: it's actually three simple rules. Underfill and you break the law; overfill and you give away margin on every single pack. Here's how to land it right.
Average weight, not minimum weight
A common myth is that every pack must contain at least the stated weight. UK law (the Weights and Measures rules, often called the average weight system) doesn't work that way. Instead, a batch of packs is judged as a whole against three packers' rules — which is why a small number of slightly light packs can be perfectly legal, while a batch that looks fine on average can still fail.
The three packers' rules
Every batch you produce must satisfy all three:
- Rule 1 — the average. The average quantity of the batch must not be less than the nominal (stated) quantity. Across the whole run, you can't be light on average.
- Rule 2 — the T1 limit. No more than 2.5% of packs may be "non-standard" — below the nominal weight by more than the first tolerable negative error (TNE), known as T1.
- Rule 3 — the T2 limit. No pack at all may be below nominal by more than twice the TNE (T2). These are "inadequate" packs and are never allowed.
What is the TNE?
The Tolerable Negative Error is the amount an individual pack is allowed to fall short of its nominal weight before it counts against you. It isn't a flat percentage — it's banded by pack size, and it gets proportionally smaller as packs get larger. A rough guide to the standard table:
| Nominal quantity (g or ml) | TNE (T1) |
|---|---|
| 5 – 50 | 9% |
| 50 – 100 | 4.5 g / ml |
| 100 – 200 | 4.5% |
| 200 – 300 | 9 g / ml |
| 300 – 500 | 3% |
| 500 – 1000 | 15 g / ml |
| 1000 – 10000 | 1.5% |
Always work from the current official TNE table for your exact pack size — the above is a guide, not legal advice.
The ‘e’ mark
The small ‘e’ you see next to the weight on many packs is a declaration that the product was packed under the average weight system and meets the three rules. It's recognised across the UK and EU, so an ‘e’-marked pack can move between markets without re-checking. Using it isn't compulsory, but if you do, you're committing to operate the system properly — including keeping records that prove it.
Many producers overfill to avoid any risk of a light pack. But if your nominal is 500 g and you're averaging 515 g, you're giving away 3% of product on every unit you make — for free. Across a year that's a serious dent in margin. The goal isn't to overfill; it's to target just above nominal and prove your batches pass.
Getting it right on the line
- Know your TNE per product. Pull the correct T1 and T2 for each pack size before you run.
- Check by sampling as you pack. Take readings through the run, not just at the end, so you can correct drift before a whole batch goes non-standard.
- Record every reading. Trading Standards can ask to see your weight records. Pass/fail evidence per batch is what keeps you covered.
- Target just above nominal. Tighten your fill so the average clears nominal with the smallest safe margin — that's where the giveaway savings are.
The bottom line
Average weight law rewards control, not caution. Learn the three rules, use the right TNE for each pack, sample as you go, and record it — and you'll stay the right side of Trading Standards while quietly stopping the daily giveaway that over-cautious filling costs you. It's one of the few compliance jobs that pays for itself.
Stop the giveaway. Stay compliant.
See TNE weight checks built into the Production app at pack-out.