The Loschmidt constant, NL, is defined as the number of particles (atoms or molecules) per unit volume of a perfect gas at STP (0°C and 760 mmHg). The accepted value is
NL is equal to the ratio of Avogadro Number, NA, to the molar volume, 
, at STP,
Note that Loschmidt constant is sometimes quoted as molar volume/molecular volume, which is the number of molecules per mole or Avogadro Number.