Density is always = mass/volume, or mass per unit volume. As for what units, that all depends upon what the items are. The more standard ones, I believe, are kg/cm3 and lbs/in3. But, there are no "set" units. It will always be mass/volume. But, the units can change.
Kg/ centimeter cube
The SI unit for density is
A centimeter cubed is equal to a mL cubed.
kg/ cm^3 or kg/ mL^3
The SI unit for density is kilogram per cubic meter (kg/m3
The SI Unit (Standard International) unit for density is
• kg/ cm^3
• kg/ mL^3
Although, these units can vary due to what is mass and volume's units because of the density formula.
D = M/ V