Why your packing list, your VGM and your freight bill show three different weights
Someone compares the packing list, the VGM and the carrier's invoice. They find three different figures and ask which one is right. All of them are right. They measure different things. The confusion causes real problems: documents get amended for no reason, and the destination queries differences that are not errors.
Net weight
The goods alone. No packaging, no pallet.
This is what your customer bought. It is usually the figure customs uses for anything charged by weight. It appears on each line of the packing list and, for some goods, on the commercial invoice.
Net weight is always lower than gross weight. If the two are equal on your packing list, someone has typed one figure into both columns.
Gross weight
Goods plus packaging plus pallet. This is what has to be lifted.
Gross weight appears on the packing list, on the bill of lading, and on almost every transport document. The destination broker compares it across the whole set, so it must be the same everywhere it appears.
The difference between net and gross is the tare. That is the packaging on its own. State it separately when the packing is heavy. A steel frame or a timber crate can explain a gross weight that otherwise looks too high for the goods declared.
Verified gross mass
This is the gross weight of a packed container, including the weight of the container itself. Under SOLAS, the shipper named on the bill of lading must certify it. Without it, the container cannot be loaded.
So the VGM is correctly higher than the gross weight on your packing list. It includes several tonnes of steel container that your cargo documents never mention. An empty twenty-foot container weighs about 2,200 kg. An empty forty-foot container weighs about 3,800 kg.
There are two ways to get the figure. Weigh the packed container. Or weigh the cargo and add the container tare shown on the plate on the door. Both are acceptable. Estimating is not.
Chargeable weight
This is the figure the carrier bills you on. It is not really a weight. It is the greater of the actual weight and the volumetric weight.
Volumetric weight converts space into a weight figure, using a divisor that depends on the transport mode. For air freight the divisor is commonly 6,000 cm³ per kg. For sea LCL, one cubic metre is usually treated as one tonne. If you ship a pallet of cushions, you pay for the space. If you ship a pallet of bolts, you pay for the weight.
This number appears on the freight invoice and nowhere else. That is why it looks like an error to anyone comparing documents. It should not appear on the packing list or the bill of lading.
Getting them to agree, where they should
Three rules cover it.
Gross weight is the same everywhere it appears. Packing list, bill of lading, and certificate of origin if it shows a weight.
VGM is higher than gross weight, by about the container tare. If it is not, either the tare was left out or the cargo weight was.
Chargeable weight appears only on the freight invoice. If it has been copied onto a shipping document, someone has used the wrong figure. A broker will stop on that.