A device for measuring the tensioning of a strap wound around one or more products or objects includes: a frame that supports a first head and a second head opposed, spaced apart and configured to receive a strap that is strapped externally to both of them; a movement mechanism for mutually displacing the heads, a detector for detecting the stress and deformation data of the strap when the movement mechanism mutually move the heads away to deform the strap until the relative breakage; a computer operatively connected to the detector, configured to process the data acquired by the detector and to calculate the values of the tensile load and of the elongation affecting the strap.