To determine the weight to calculate the customs duty you need to take into account domestic specificity.

In some countries, which include Russian Federation, the calculation of the customs duty in the weight include the weight of interior packing. Russian customs accepts the weight the weight of product in the packaging in which the commodity goes to the consumer. It is important to consider if you want customs duties.
While the same goods in the weight in the outlets are produced in a separate location simultaneously with the opening of the container and definitely not later than 10 days (for perishable goods no later than 24 hours) of receipt of goods. The tare weight is checked simultaneously with the net weight of the goods.
Check the net weight in the order specified in standards, technical conditions and other stipulated by both parties rules. If you can't weigh the product separately from packaging at the time of acceptance for various objective reasons, the weight is determined by subtracting weight of the empty container (after her release) of the weight of the gross receipt of the actual weight of the goods. The weighing results you need to issue the relevant acts.
To determine the net weight by subtracting tare weight from the gross weight according to the transport and accompanying documents, without verification of the actual gross weight and the tare weight guidelines are not allowed.
And finally, a few words about the technical side of the issue. Now there are many scales designed for industrial measurement. In many models there is a function to determine the net weight, i.e. excluding the weight of the package. On such scales weigh the container, then the container with the cargo. The scale automatically calculates the weight. Another convenient option – when the terminal can at any moment toggle the screen indicators weight net, gross and tare.