For the USA I would suggest to look into the guidelines by the National Institute of Standards and Technology (NIST) regarding MAV.
(1) Batch Average
The average net product weight of the packages in each finished product batch must equal or exceed the labeled net weight.
(2) Individual Package
The variation of individual package contents from the labeled quantity must not be “unreasonably large”. The variation between individual package weights with any given batch must not exceed a specified range depending on the net weight claimed on the package.
The Maximum Allowable Variation (MAV) is the limit of “reasonable Variation” for an individual package base on the NIST Handbook 133. For determining the MAV for each package size reference Table 2-5 in Appendix A of NIST Handbook 133 - 2013 Edition, http://www.nist.gov/...bs/hb133-13.cfm.
Example: Based on Table 2-5, a 20 Kg (44 lbs.) bag has an MAV or +/- 226 g (0.50 lbs.)
Local Work Instructions should provide the MAV for each package size filled at that location.