This article reports on the realization and on first applications of the Cadyts (“Calibration ofdynamic traffic simulations”) calibration tool. The presented first version of Cadyts calibratesdisaggregate demand models of dynamic traffic assignment simulators from traffic counts. Thetool is broadly applicable in that it (i) makes only very mild assumptions about the calibratedsimulator’s workings and (ii) allows for various modes of technical interaction with the simulationsoftware. The article provides a both conceptual and technical overview of the tool andexemplary demonstrates its applicability to two different traffic microsimulators.