Volume is the measure of how much space an item takes up. Bulk storage containers show volume and not kg.

The volume of a single item can be determined by adding it to a bulk storage container (bulk storage bin, food storage bin) and looking at the volume value.

Unique items (ex: tools, armor, weapons; non-resource items) cannot be be stored in a volume based container.

Kg is the abbreviation for kilograms. Kilograms measure the weight (also known as mass) of an item.

Liquid is also measured in grams and kilograms. A measuring jug is used to measure out precise weights of liquid. In the case of liquids, 1kg is equivalent to 1l (liter) in WU.

The weight of a single item in kg drag it to your inventory, or to a container that shows kg and not volume (typically anything but a bulk storage container).