Confusing g/cm³ and g/l

Grams per cubic centimetre and grams per litre are the same, because both are built on grams.

The difference is a factor of 1000: 1 g/cm³ = 1000 g/l. A density figure in g/cm³ is therefore three orders of magnitude below the same value in g/l. Only g/l and kg/m³ are numerically identical.

Both spellings contain a gram and a volume, just with a different reference volume: a cubic centimetre is one thousandth of a litre. Because water has a density of about 1 g/cm³ the figure looks familiar, and the factor of 1000 is overlooked.

Watch the reference volume in the denominator: cm³ means the value sits a factor of 1000 below the same figure in g/l. For water 1000 kg/m³ = 1000 g/l = 1 g/cm³; for air about 1.2 kg/m³.