Refers to the weight of a product excluding packaging, container, or wrapping. Common in commercial, shipping, and food contexts.
The net weight of this canned food is 200 grams.
総重量 means 'gross weight' (total weight including packaging), while 正味重量 is the weight of the contents alone.
Compound of 正味 (しょうみ, 'net, actual content') and 重量 (じゅうりょう, 'weight'). The term is straightforward and transparent.