This paper presents calculation model enabling determination of the leakage rate in labyrinth seals. Described model is based on the Saint-Venant equation. It includes a new type of flow coefficient, which was determined based on experimental tests and described depending on the Reynolds number and the radial clearance. The structure of this calculation model can be applied to determine the leakage rate in straight through, staggered labyrinth seals as well as with various number of clearances. This model enables determining distribution of thermodynamic and flow parameters of the gas along the seal length. Results obtained from this model were next compared with experimental data for various types of seals. It enabled determination of kinetic energy carry-over coefficient in geometries under investigation. The value of this coefficient was then compared with the value of the coefficient from the Scharrer’s, Neumann’s and Hodkinson’s models. Obtained results indicate that the value of the kinetic energy carry-over coefficient depends not only on the seal geometry, but also on the pressure decrease.