Left : sketch of the accretion efficiency determined by Liu & Ormel (2018). Individual pebbles simulated either hit the planet and accrete or pass by the ring at r = a_pl. The efficiency is calculated using Eq. (15). Right : sketch of the accretion efficiency, as determined by our method. The dust radially drifts inwards with a mass flow Ṁ, calculated at two rings located at a_in and a_out using Eq. (17). The efficiency ε is subsequently calculated using Eq. (16).