Thin films with low adhesion and large residual stresses may buckle. The resulting morphologies are varied, but one of the most commonly observed is an intriguing oscillating pattern – the so-called "telephone cord" – which has been extensively investigated in the recent years. We have studied the kinematics of formation of telephone cords using a geometrically non-linear plate model and mode dependent interfacial toughness, captured via a cohe-sive zone. Through extensive Finite Element Simulations, we have demon-strated a simple, non trivial relation between telephone cord wavelength and interfacial toughness. To validate this prediction, highly stressed Mo thin films where deposited on Si wafers, with a well defined interface and very reproducible adhesion. Studying the morphology of the resulting buckles for different film thicknesses and stresses, we observed a trend which was fully consistent with our simulation results. From the data fit, an adhesion energy of 0.58 ± 0.04 Jm −2 for the SiO 2 /Ag interface was inferred, which compares well with literature estimates.