This article explores a method for determining the concentration of graphene dispersion using the integral optical technique based on the Beer-Lambert-Bouguer law for direct ultrasonic exfoliation method. The results showed nonlinear dependence of conductivity on concentration, indicating fundamental differences in the mechanism of exfoliation at different solid phase concentrations. Graphene dispersions in ethylene glycol also exhibited low transmittance in the visible region of the spectrum, which requires the use of other research methods for higher concentrations. Extinction coefficients were determined to calculate the concentration of graphene in the dispersion, which allows for the calculation of light absorption in the solution at a certain concentration and beam path length. The obtained results can be useful for further use of graphene in optoelectronic devices. Additionally, the concentration of few-layered graphene particles was calculated in the suspension obtained by liquid-phase exfoliation method with an initial graphite concentration of 6 mg/ml.