Abstract A formula to evaluate the density of liquids was suggested on the basis of the molecular–statistical theory of liquids according to the distribution function. The regularities of changes in density were estimated in different ranks of normal (non-associated) liquids. It was shown that association leads to increase in density. Certain criteria were proposed, which allowed to assume the presence of association on the basis of density of a liquid. The characteristics of density of liquids consisting of molecules with intramolecular hydrogen bond were established. The density values were estimated for 36 compounds at 404K (or 445K).