This paper devoted to problem of correct inductance calculation for electrical coil into finite non-conductive space. The task is solved by means of finite element method as a well-known approach to calculate magnetic field for different cases. The problem is considered in the two-dimensional Cartesian space. As a result, numerical calculations of coil inductance are compared with analytical ones for different aspect ratio of conductor cross-section size and whole calculated area. The considered approach of coil inductance calculation shows divergence with analytical solution does not exceed of 0.2%. Finally, quantitative mark of sensitivity of calculation accuracy dependent on calculate domain size are provided.