Equations are proposed for calculating the molar volume of liquid hydrocarbons used in production of surfactants. With such data, it will be possible to calculate most of the physicochemical properties of these hydrocarbons to solve many process problems.In chemistry and chemical engineering, data on the physicochemical properties of the compounds involved are used in any technical calculations. The search for these data has become an independent problem and is frequently not successful, due to the absence of published data, for example, for higher alkylbenzenes and alkylphenols, widely used as feedstock for production of surfactants -additives to petroleum products and detergents.Despite the important advances in theoretical physics, a generalized theory which would allow reliably calculating the indexes of the properties of solids and liquids has not yet been created. Especially great difficulties arise in calculating the indexes for the properties of liquids. For this reason, the search for sufficiently adequate empirical or semiempirical relations that could be used to calculate the indexes of the properties of a compound acceptable for practice based on minimal initial information is just as pressing as before.The molar volume (or molar density) of a substance is one of the fundamental properties used in calculations, from the energy of formation of a hole in the theory of the liquid state of substances to the reaction volume in liquid-phase processes in chemical engineering, for example. This volume (cm 3 , liters, m 3 ) is occupied by 1 mole of a substance.The molar volumes differ at 20°C (V), the boiling point (V b ), and some temperature t between the melting and boiling points of the substance (V t ). They are either calculated with the existing experimentally determined molecular mass M and density r of the compound at a given temperature (V = M/r) or the additive method.