The present invention refers to a spring forming device (1) comprising: a system (3) for feeding a wire (4) for forming a helical spring (2); a winding system (7) suitable for winding said wire (4) according to a helical configuration having a predefined diameter (D) extending along a helix development axis (A); one or more pitch tools (11, 13, 9), each suitable for acting on the wire (4) so that it takes on said cylindrical helix configuration with a predefined pitch (p); a system (15) for detecting the actual pitch of the spring forming in device (1) starting from said wire (4); means for detecting the amount (I) of the fed wire; a control unit configured for: determining the actual length (Leff) of the spring forming in the device starting from the actual amount of the fed wire (I) and actual pitch (peff) detected for portions of the spring, already formed in the device; determining a reference length (L) as a function of said actual amount (I) of fed wire; determining an error between said reference length (L) and said actual length (Leff); generating a command signal such to vary, during the spring formation, the configuration of one of said one or more pitch tools (11, 13, 9) as a function of said error. Moreover, the present invention refers to a method for forming springs and a corresponding computer program.