The invention relates to a method and to a corresponding device for filling at least one seat cushion (12) of a seat (10) with, and emptying same of, a fluid, in which, during a filling or emptying operation, depending on a switching state of an actuating member (16) designed for filling or emptying the at least one seat cushion (12), a first pressure value (pin) determined upstream of a throttle point (20) through which the fluid flows, and a second pressure value (pout) determined downstream of the throttle point, are detected, and, depending on the first pressure value (pin) and the second pressure value (pout), an estimated value (m_EST) of a mass of fluid supplied to or removed from the at least one seat cushion (12) is determined.