TPC. Tonnes per Centimetre Immersion.If the vessel is loading in salt water and the freeboard is checked it may be found that more cargo can be loaded to immerse the ship another few centimetres.
It is useful to convert this to tonnes. This is the TPC. The TPC varies with the draught and with the water density. Changes in draught cause a change in displacement and the TPC assists in calculating the change. TPC can be calculated by the formula:
TPC = (A) x (d) /100
where A = area of water plane at a certain draught
d= density of water in which the ship floats.