Abstract <p>The article presents a method for calculating the interphase surface area in a gas–liquid apparatus with ejection gas dispersion. The apparatus is divided into three phase contact zones: the injection zone (free torch zone), the ejection zone (constrained torch), and the working volume. The geometric surface area of phase contact is calculated for all zones of the gas–liquid apparatus with ejection gas dispersion. The specific surface area of phase contact is calculated for each zone and compared. Based on experimental data, the geometric surface area of phase contact is determined for the working volume and the effective area for the entire gas–liquid apparatus. The calculated and experimental values of the surface areas of phase contact are compared.</p>