I have seen two numbers for coal density

40 ft

833 kg/m

You need to decide what depth you want to fill it to, then figure square footage based on the required volume:

A = 40 ft

For any given depth of container, a square container will require the least area in the sides of the container. A cubical bin for a ton of coal made using the rule of thumb would be about 41 inches on each edge. Be mindful of the weight and the corresponding structural requirements.

40 ft

^{3}/ton (rule of thumb for coal bunkers) (801 kg/m^{3})833 kg/m

^{3}(bituminous, broken) (38.5 ft^{3}/ton)You need to decide what depth you want to fill it to, then figure square footage based on the required volume:

A = 40 ft

^{3}/(depth in feet)For any given depth of container, a square container will require the least area in the sides of the container. A cubical bin for a ton of coal made using the rule of thumb would be about 41 inches on each edge. Be mindful of the weight and the corresponding structural requirements.