Disclosed are systems, devices and methods for detecting and measuring TMS-induced electrical fields. In accordance with certain aspects of an embodiment of the invention, a TMS sensor probe is provided having a field detector, a first electrical connection connecting the field detector to either a power source or a processor, and a second electrical connection connecting the field detector to a processor. The field detector is configured to measure a characteristic of a TMS-induced electrical field at the location of the field detector, and the processor is configured to receive the measured characteristic of the induced electrical fields and display a human-readable depiction of a calculated induced electrical field. A system using such a sensor probe to calibrate a TMS-induced electrical field is also provided, including the foregoing sensor probe, and a magnetic field generator.