Paying weight was created as a conversion factor for air freight in order to bridge the difference between volume and weight. After all, 1,000 kilos of feathers requires a larger volume than 1,000 kilos of lead. So as to be able to charge this difference equally, a conversion factor was called into life.
With air freight, 1 cubic metre equals 167 kilos. With seaborne freight LCL, 1 cubic metre equals 1,000 kilos, while with road transport 1 cubic metre equals 333 kilos (measuring 3 times). The highest weight (volume or actual) is charged.