We describe how the out-of-plane dielectric polarizability of monolayer graphene influences the electrostatics of bilayer graphene - both Bernal (BLG) and twisted (tBLG). We compare the polarizability value computed using density functional
theory with the output from previously published experimental data on the electrostatically controlled interlayer asymmetry potential in BLG and data on the on-layer density distribution in tBLG. We show that monolayers in tBLG are described well by polarizability αexp = 10.8 Å3 and effective out-of-plane dielectric susceptibility ϵz = 2.5, including their on-layer electron density distribution at zero magnetic field and the interlayer Landau level pinning at quantizing magnetic fields.