Abstract: System for charging the use of a packet based telecommunication network. A measuring device (2) measures the number (n) of data units during a period of time (T) or the period of time (t) between a certain number (N) of data units. At any rate, the period of time is short in relation to the total connection time. A calculation device (4) calculates per period of time the number of data units per unit of time and transmits that calculation result (r) to a billing system (5). If the telecommunication system comprises system data units which comprise an indication (r1) of the capacity or priority requested by the user, that indication can also be passed on to the billings system, as well as an indication of the capacity or priority assigned by the telecommunication system.