The present invention relates to a lens edge simulation tool (10) for measuring the fitment of a lens edge profile (LEP) with respect to a frame groove profile (FGP) of a spectacle frame (20), the lens edge simulation tool (10) having a defined edge profile (STP) like a lens edge profile (LEP) of a lens (6) being machined by a defined edger machine (4), the defined edge profile (STP) comprising a bevel portion (11) protruding towards a protrusion direction (A), wherein the lens edge simulation tool (10) further comprises a probe (15) provided at a distal end tip portion (14) of the bevel portion (11) and being moveable (M) along the protrusion direction (A) between a retracted position in which the probe (15) does not protrude from the defined edge profile (STP) and an extension position in which the probe (15) protrudes from the distal end tip portion (14). The present invention further relates to a system (1) and method for defining a lens shape for a machined lens (6) adapted to fit into a frame groove (21) of a spectacle frame (20).