Load density of a cargo tank defines how much cargo we can load in a tank. This depends upon how strong the tank top is. The load density of a tank is provided by the class during yard delivery of the ship.

For dry cargo ships the load density of the tank top is given in t/Sq Meter. That is how many tonnes can be loaded in one square meter of tank top area.

Let us take a simple example. Say load density of tank top of a bul carrier is 12 tonnes/sq meter. The length of the cargo hold is 30 meters and breadth of the cargo hold is 20 meters. So how much total cargo we can load in this tank.

Total cargo that can be loaded in this tank = Length x Breath x Load density

So Maximum cargo = 30 x 20 x 12 = 7200 Tonnes.

Now if the stowage factor of the cargo to be loaded is 0.9 m3/Tonne.

So the volume of the cargo that can be loaded in tank will be 7200 x 0.9 m3. That mean we can load 6480 m3.

We know the length and breadth of the tank, so we can calculate the maximum height to which this cargo can be loaded.

Maximum Height = 6480 / 600 = 10.8 Meters

So load density helps the ship staff to know to what height a cargo can be loaded.

On tankers, load density is given as to the maximum density of the cargo that can be loaded.

For example, if load density of a tanker ship is given as 1.2 t/m3, it means that we can load the tank to full if the load density is lesser than or equal to 1.2 t/m3.

Let us say that volume of the tank is 3000 m3. This means that in this tank we can load maximum 3600 tonnes (3000 x 1.2 tonnes). Now it does not matter which cargo we load, we can never load more than 3600 tonnes of cargo in this tank.

Now if we have to load a cargo of density 1.4 t/m3, we can load only 2571 m3 (3600/1.4 m3) of this cargo. From the ullage table (or sounding table) we can calculate to what level we have to load this cargo.