cm⁻³
per cubic centimeter
Number densityexact by definition
The reciprocal cubic centimetre equals exactly 1e6 reciprocal cubic metres, since a cubic centimetre is exactly 1e-6 cubic metres. It is the customary unit in semiconductor doping, aerosol and particle counting, and plasma physics, where dopant concentrations run from about 1e14 to 1e20 per cubic centimetre. The conversion is exact, following from the exact definition of the centimetre.
Watch out: Cleanroom classifications and air quality standards often count particles per cubic foot or per litre rather than per cubic centimetre, and the particle size threshold matters as much as the count. A number without a stated size cutoff cannot be compared to another.
| 1 cm⁻³ | 1,000,000 m⁻³ |