Left panel: influence of the ice mass fraction f_ice on the radius. The reminder of the mass has a rocky composition. Radii are plotted for planets of M = 0.1   M_⊕ (red solid line), 1 M_⊕ (green dotted line), 10 M_⊕ (blue dashed), 100 M_⊕ (magenta dashed-dotted), and 1000 M_⊕ (cyan short-long dashed), all without an external pressure. The thin black short-dashed-dotted line is for a 10 M_⊕ core of an old 1 M_X giant planet, and the thin black long-dashed-dotted line is for the 10 M_⊕ core of a 10 M_X giant. Right panel: radius as a function of external pressure P_ext for pure ice planets. The (thick) lines represent the same planet masses as in the left panel.