Measurements from proton-proton collisions at centre-of-mass energy of $\sqrt{s} = 13$ TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. The observed distributions are corrected to well-defined phase-space regions ($p_\text{T} > 500$ MeV and $|\eta| < 2.5$ of the particles), using model-independent corrections.