Method for determining weight of an occupying item of a seat in a vehicle having a seat cushion assembly and a seat back assembly defining a contact surface adapted to be in contact with the occupying item of the seat in which a support structure is arranged underneath the seat cushion assembly to support the seat on a substrate in the vehicle. The support structure transfers a force exerted by the occupying item on the support structure to the substrate. At least one strain measuring transducer is mounted at a respective location on the support structure to provide a measurement of the strain in the support structure at the location at which it is mounted. The weight of the occupying item of the seat is determined based on the strain in the support structure measured by the strain measuring transducer(s).