We present here an unprecedented way of quantifying the number of dislocations in microcrystals. This method relies on a combination of several state-of-the-art techniques: coherent x-ray diffraction used as a local probe, together with the controlled compression of micro-objects. We demonstrate that by using this method, dislocations in the microcrystal can be detected and their number precisely quantified. This cannot be done with other techniques in a nondestructive way. Our method opens a route for the study of many small-scale systems with defect-dependent physical properties and it could become a critical tool for addressing future challenges in nanotechnology.