A seatbeltsystem for adapting to a seat occupant's body an inflatable seatbelt of a seat of a vehicle. The invention relates to a seatbelt system (32) for adapting an inflatable seatbelt (33) to a seat occupant (30) comprising: - a vehicle seat (31), - An inflatable seatbelt (33) comprising at least one cushion layer (33a) into which a gas is introduced, a belt buckle (34), a shaft rotation (35) and a return spring (36), - A gas generator for supplying a gas into the at least one cushion layer (33a) of the inflatable belt (33), - At least one sensor (37, 38, 39, 40) located in the seatbelt system (32) for determining the presence and the body shape of the seat occupant (30) on the seat (31) configured to generate one or more signals indicative of at least one parameter associated with presence and the body shape of the seat occupant (30), - A controller (22) capable of receiving the one or more signals associated with the presence and a body shape of the seat occupant (30) on the seat (31) and analysing the received one or more signals and processing the inflation of the at least one seatbelt cushion layer (33a) while driving based on the analysis.