The climate effect of contrails depends on the contrail lifetime. Thus, it is important to know what constrains the lifetime. In this paper, we characterise the two most important contrail dissolution processes via their respective timescales. Both timescales are in the order of a couple of hours, depending on the synoptic situation and the size of the contrail ice crystals. The combined timescale, which combines both processes, is the harmonic mean of the two single timescales.