Frequency is the defined as number of complete cycles per second.
Mathematically,
Frequency = number of vibrations/sec
Dimensional Formula of Time = M0L0T1
Putting these values in above equation we get
Dimensional Formula of Frequency = 1/ M0L0T1 = M0L0T-1
Hence,
Dimensional Formula of Frequency = M0L0T-1
SI unit of Frequency is the hertz.