Growth timescale t_growth as function of planetesimal radius R for a constant internal density ρ_• = 1 g cm^-3. Crosses indicate numerical data, while the solid lines are fits. The color scale extends from dark blue to light blue, transitioning from lowest particle radius to highest particle radius. a) t_growth obtained with the potential flow solution at 1 AU orbital distance and a pebble density of ρ_p = ρ_g/ 100, showing maxima at R_gr,max ~ 100 km. b) t_growth with the Stokes flow solution at 1 AU orbital distance and a pebble density of ρ_p = ρ_g/ 100 , showing early settling and flattening out of the curves. c) t_growth with the potential flow solution at 3 AU orbital distance and a pebble density of ρ_p = ρ_g/ 100. d) t_growth with the potential flow solution at 10 AU orbital distance and a pebble density of ρ_p = ρ_g/ 100 (top, blue) and a pebble density of ρ_p = ρ_g (bottom, red).