Comparison between single- and full-size coagulation calculations. The solid lines show the snapshots of the peak mass m_p (Eq. (A.9); upper panel) and total dust surface density Σ_d (Eq. (A.8); lower panel) at different times as a function of orbital radius r obtained from the full coagulation simulation for the compact aggregation model by Okuzumi et al. (2012, see also their Fig. 2). The dashed line shows our reproduction using the single-size approach (Eq. (4) for Σ_d and Eq. (5) for m_p) with ϵ = 0.5 (see Sect. 2.4 for the definition of ϵ).