In most cases, the rate charged is based on the net registered tonnage of the vessel; the current charge is 41 pence per net registered ton.

Shipping fees would increase to 24 cents, from 9 cents, for a net registered ton on vessels entering the United States from a foreign port in the Western hemisphere and to 71 cents, from 27 cents, from other foreign ports.

Whereas Gunnar Knudsen's ships had a total carrying capacity of 8898 net register tons between them, Jørgen Christian Knudsen and his son's ships had a capacity of only 3885 net register tons altogether.