In physics weight is defined as the product of mass and acceleration. It is the force with which the earth attracts the body towards its centre.
Mathematically,
Weight = Mass x Acceleration.
Dimensional Formula of Mass = M1L0T0
Dimensional Formula of Acceleration = M0L1T-2
Putting these values in above equation we get,
Dimensional Formula of Weight = M1L1T-2
SI Unit of Weight is newton (N) or Kg.m.s-2