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Average Weight Requirements Explained

Last Updated: September 5th, 20235 min read
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Average weight is a complex topic that can be difficult to understand, so for that reason, we have devised this blog to explain what it is and if it applies to your business.

If you produce and sell packed food products based on weight, it is a legislative requirement to adhere to the Weights and Measures Act enforced by Trading Standards.

The act dictates requirements on units of measurement, specified quantities, packed goods, equipment and records, and labelling of packaged goods.

What does the legislation require?

When selling packaged food products based on their weight or volume, the product must be packed using either the minimum weight system or the average weight system.

What is the minimum weight system?

The minimum weight system means products are packed against the declared weight on the label. The weight of the product can be more, but not less than the declared weight.

This method is suitable where a low volume of products is being produced, as each packed product is weighed and checked individually for compliance. As a result though, this system can result in more product giveaway.

What is the average weight system?

When dealing with larger batches, it’s more appropriate to use the average weight system, where products are packaged to a measured average – the nominal weight. This average is calculated through sampling or sample weighing for example.

Sampling is the process of measuring a certain number of products (a sample) from the batch to determine an average weight or volume. The necessary method and frequency of sampling for your business will be stipulated by trading standards.

If your business is using the average weight system, you must make sure you follow the three packers rules (below). Manual sampling can be labour intensive and records need to be kept for evidence of due diligence too.

This is why we recommend using a static or dynamic checkweighing solution, which will massively speed up the process and eradicate the risk of human error in your measurements.

For static checkweighing, our own Average Weight System will automatically record your sample weighing data, with electronic reports available at the touch of a button for easy evidencing.

For more robust dynamic checkweighing, which will go further and check every single product on your line we recommend a checkweigher, which will handle rejects automatically too.

What are the Three Packers Rules?

Rule 1: the average weight of a batch must meet or exceed the nominal weight of the batch.

Simply put, the average weight of products within a batch needs to be the same, or greater, than the weight labelled on the packaging (nominal weight).

To work out if your batch complies with rule 1, you need to:

  • Add up all the weights of the sample products.
  • Then divide the total weight by the number of samples.
  • This gives you the average weight of the batch, which must meet or exceed the nominal weight.

For example…

You need to sample 3 products from your latest batch. The nominal weight of your product is 250g. Your 3 sampled products weigh in at: 248g, 254g, 251g.

248 + 254 + 251 = 753g total
753 divided by 3 = 251g average weight

251g exceeds the 250g nominal weight, so this batch passes rule 1.

Moving on to rules 2 and 3, you should first know what a tolerable negative error is…

Okay, so what does tolerable negative error (TNE) mean?

When weighing packaged food products, they must not be less, on average, than the weight declared on the label.

As per the table below, a small number of packaged products CAN fall below a certain margin of error, the tolerable negative error (TNE), and no package can be underweight by more than twice the TNE.

T1 = 1x the TNE

T2 = 2x the TNE

Try our T1 and T2 weights calculator!

Looking to work out what your T1 and T2 weights might be? Our calculator will automatically calculate your T1 and T2 weights based on the target weight.

Rule 2: there must be no more than 2.5% of significantly underweight samples or weights (T1 samples).

This rules states that a batch must not have more than 2.5% (or 1 in 40) T1s in a batch. The table above allows you to calculate the TNE based on the nominal (declared) weight of your packed product.

The example below shows a failed batch. Of the 10 sampled products, 3 are T1s. This is 3.33% of the sampled products, which is higher than 2.5%.

As a result, this batch fails to comply with rule 2.

Rule 3: there must be no extremely underweight samples at all (T2 samples).

The third rule stipulates that there must be no underweight (T2) samples in your batch. To calculate your T2, it’s simply your TNE x 2.

Using the same nominal weight as an example once again, a T2 would be any product that falls below 232g.

The graph below shows an example of a failed batch, due to the presence of a product that weighs 230g – making it a T2.

To satisfy average weight legislation, you must provide evidence that your batches comply with the three packers’ rules. As mentioned previously, this can be done manually or automatically using an electronic, static average weight system or dynamic checkweighing solution.

What else do I need to know?

What is the e mark?

The ‘e’ mark is printed on product packaging to indicate that the product is packed in accordance with average weight requirements, including complying with the three packers rules.

While there is no legislative requirement to include the mark on your product packaging, you may be required to do so by your retail partners and stakeholders. It is also a good indicator of your product being responsibly manufactured for market.

Keeping Average Weight records

You must keep records of your sample batches for a minimum of one year based on the date the packet is shipped or the ‘use by’ date, whichever is shorter. These records must show that the Three Packers Rules have been met.

Weighing equipment requirements

You must ensure the equipment you use is suitable to meet Trading Standards’ requirements, for example, a domestic scale would not be suitable, the scale you use must be Trade Approved and stamped accordingly. Trading Standards will check the weights and measures of your goods on your production line.