The Kennicutt-Schmidt Law (Kennicutt-Schmidt Relation, Schmidt Law or Star Formation (SF) Law) is an empirical relation between a region's Star Formation Rate (SFR) and its gas density, saying the SFR is proportional to a power of its gas density, i.e.,
ΣSFR ∝ ( Σgas)n
Where ΣSFR is the SFR, Σgas is the gas density, and n is a constant, currently estimated to be 1.4 if the SFR is in Solar masses per year per square Parsec (pc) and gas density is grams per square parsec.
The law is seemingly oddly given in terms of Surface Density (Σ) rather than volume density.
Surface Density (Σ)