Zerodor sphere density artefact.

The derived SI unit of density is mass per unit volume (kg·m^-3). Conversion factors to non-SI units may be found here.

The density of a solid or liquid may be fundamentally determined by hydrostatic weighing using Archimedes' principle. These measurements are traceable to either the density of pure water or to a solid density artefact.

There are numerous other density measurement techniques including hydrometry, pycnometry and the use of vibrating cell meters, to name but a few.