A tape drive comprising: first and second motors; first and second spool supports, respectively receiving first and second spools of tape, the first spool support being driveable by the first motor and the second spool support being drivable by the second motor; a sensor arranged to provide a signal indicative of linear movement of tape between the tape spools along a predetermined tape path; a controller arranged to control energization of said first and second motors for transport of the tape in at least one direction between the first and second spools of tape along the predetermined tape path; wherein the controller is arranged to generate data indicating the diameter of said first and second spools of tape based upon said signal provided by the sensor and data indicating rotation of each of said first and second spools.