  A measurement of the inelastic proton-proton cross section at a
centre-of-mass energy of $\sqrt{s}$ = 13 TeV is presented. The analysis is
performed using the CMS detector, in particular with information from forward
calorimetry at pseudorapidities of 3.0 < {\eta} < 5.2 and -6.6 < {\eta} < -3.0.
A visible cross section is measured in two different detector acceptances and
finally extrapolated to the full inelastic phase space domain. The results are
compared with those of other experiments, and with models used to describe
high-energy hadronic interactions.
