Abstract: The invention provides a method and an apparatus for determining the bending angle of a work piece to be bent by means of a bending apparatus comprising a punch member and a die member cooperating with the punch member. The die member is provided with at least two channels through which pressurized air is blown towards a leg of the bent work piece. For measuring the pressure in each of the channels, a plurality of pressure sensing devices is provided and connected to a common control and analyzing assembly. On the basis of the pressure values measured by the pressure sensing devices and with the aid of formulae, tables, three dimensional diagrams or with the aid of a neuronal network, the control and analyzing assembly calculates the bending angle.