Net Content Verification: Metrological Inspection of Pre-Packaged Goods
What Are the Net Content Rules?
The net content of pre-packaged goods is inspected per JJF 1070: take n samples, weigh gross and tare to obtain actual net contents, and require (1) the average actual net content to be greater than or equal to the labeled net content, and (2) each item's actual net content to be no less than the labeled value minus the allowable shortage T. Both conditions must hold for the lot to pass. Net content is a core indicator of metrological supervision for pre-packaged goods and directly affects consumer rights and compliance risk; consistently meeting it is the foundation of compliant operation.
How to Find the Allowable Shortage T
JJF 1070 defines T by bands of labeled net content (for example, a band of 1 to 50 g allows a shortage of 9%, with the exact value from the table) and distinguishes two tiers, shortage and serious shortage. The tool has the T band table built in: enter the labeled net content and it takes T automatically and applies the dual judgment for per-item shortage and average content. The T table follows the current revision of JJF 1070, and the tool executes the current version and marks the band.
Sampling and Judgment Procedure
Take the sample size n from the JJF 1070 annex (it depends on the lot size), weigh each item and determine the tare, and calculate the per-item actual net content and the lot average. Then apply the two rules: average content >= labeled value, and per-item shortage <= T. The tool judges a batch of data in one pass and counts nonconforming items. Sampling should be random, weighing equipment must meet metrological accuracy requirements, and tare determination must be accurate; follow the standard strictly at every step to avoid misjudgment.
Precautions
Determine the tare per the standard (weigh after removing packaging). Net content means the quantity of the contents after removing packaging, which is different from gross weight. Testing conditions (temperature, moisture absorption) affect weighing results. A lot judged nonconforming can apply for re-inspection, and the re-inspection rules follow the standard, so keep filling records and cross-check gross weight, tare and records to make the final conclusion more reliable.