In the context of GEOLAB project, a series of pile tests will be conducted at the geotechnical testing pit of the Institute of Geotechnics at the Technical University of Darmstadt. These experiments involve subjecting the steel pile to horizontal loading. The pile is equipped with a total of 16 strain gauges, distributed along its length, to capture the bending moments and strains during the experimental tests. To accurately analyse the experimental data the strain gauges should be properly calibrated. The calibration process of the strain gauges is carried out by performing three-point flexural test on the pile.