Collapse time as a function of solid planetesimal radius for clouds with initially monodisperse mm-, cm-, or dm-sized pebbles. Power-law fits to the data and the free-fall time of the initial cloud (t_ff ~ 25.1 yrs) are added to the plot. For small planetesimals (≲50 km) the collapse time is inversely proportional to the planetesimal radius and increases linearly with the pebble size. This is the same relation as we find in Appendix A where we assume bouncing as the only collisional outcome. For larger planetesimals (R_solid ≳ 50 km) the collapse time drops rapidly as pebbles fragment and the number density and collision rates increases. The collapse time is, however, limited downwards by free-fall, so for even larger planetesimals with R_solid ≳ 70 km the collapse time is equal to the free-fall time of the initial cloud.