The sea freight is priced to several levels according to the commodities’ nature, category and the difficult level of loading and keeping. Different commodities, different basic freight. The category and type of the cargo influence the freight a lot.  

Counted by weight, shown as W
Counted by volume, shown as M
Counted by weight or volume according to the liner company, shown as W/M
Counted by the FOB value, called Advalorem, shown as AdVal or A.V.
Counted by mixed methods, such W/MplusAV

Besides, some goods are counted by per unit or per head, like car by unit, live poultry by head. Some bulk cargo freight can be discussed between the parties as the quantity is quite numerous and easy to load, such as grain, mineral, coal and etc.

Calculating the freight is a complex job requiring intimate knowledge of freight index, carefulness and patience. After Basic Rate is obtained, the related surcharges need to be added.

There are quite a number of surcharges, which are paid according to the commodity type, the posts of departure and destination and etc. And some would be contemporarily charged.

What should attention be paid to is that some of surcharges take a great part of the total shipping cost, some may be twice as much as basic rate. Therefore, surcharges must be noticed when calculate the freight.