Abstract: A method is disclosed for determining the start pressure within a gas tank (4) to be refueled, said method comprising the steps of connecting the gas tank (4) to a dispenser volume (3) of a dispenser unit (3, 5-7, 10, 11), which volume (3) is significantly smaller than the volume of the gas tank (4) to be refueled, applying a pressure to the gas in the dispenser volume (3), which pressure is equal to or higher than the pressure within the gas tank (4), so that gas start to flow from the dispenser volume (3) into the gas tank (4) through a check valve (9), which is a part of the gas tank (4), and determining the start pressure by measuring the pressure at the interface (8) between the dispenser unit (3, 5-7, 10, 11) and the gas tank (4).