The paper presents approximate formulas for parameterizing the coefficient of light absorption by phytoplankton a ph ( λ ) in Baltic Sea surface waters. Over a thousand absorption spectra (in the 350–750 nm range), recorded during nine years of research carried out in different months of the year and in various regions of the southern and central Baltic, were used to derive these parameterizations. The analysed empirical material was characterized by a wide range of variability: the total chlorophyll a concentration ( Tchla ) varied between 0.3 and > 140 mg m −3 , the ratio of the sum of all accessory pigment concentrations to chlorophyll a ( ΣC i / Tchla ) varied between 0.21 and 1.5, and the absorption coefficients a ph ( λ ) at individual light wavelengths varied over almost three orders of magnitude. Different versions of the parameterization formulas were derived on the basis of the data gathered: a one-component parameterization in the classic form of a power function with Tchla as the only variable, and a two-component formula – the product of the power and exponential functions, with Tchla and ΣC i / Tchla as variables. There were distinct differences between the general version of the one-component parameterization and its variants developed for individual months of the year. In contrast to the general parameterization, both the monthly and the two-component variants enable, at least partially, the variability of pigment composition occurring throughout the year in the Baltic phytoplankton populations examined here to be taken into account.