The meter cubed per kilogram (symbolized m 3 /kg) is the standard unit of specific volume in the International System ( SI ). It is expressed directly in base SI units, and cannot be further reduced. Specific volume is the reciprocal of density .
A substance with a specific volume of 1 m 3 /kg is extremely large for its mass. In fact, air at sea level has a specific volume less than this. Materials with high density have low specific volume; materials with low density have high specific volume.
Alternative units are often used to express specific volume. The most common of these is the centimeter cubed per gram (cm 3 /g). A substance with a specific volume of 1 cm 3 /g has a specific volume of 0.001 m 3 /kg. Conversely, a substance with a specific volume of 1 m 3 /kg has a specific volume of 1000 cm 3 /g.