  We study capacitance of the 2D topological insulator (TI) edge states. The
total capacitance is combined as a serial circuite of 3 capacitors presenting
geometrical $C_G$, quantum $C_Q$ and correlation $C_{corr}$ contributions to
the electron energy. If the Coulomb interaction is weak, they obey an
inequality $C_G<C_Q<C_{corr}$. Quantities $C_G$ and $C_Q$ are found in the case
of a round TI dot. The quantum capacitance at the finite temperature is
determined taking into account the edge states quantization with and without
the magnetic field. We have concluded that, in the accepted approximations,
$C_{corr}=0$.
