Difficulty driving large currents through an inductive load at high frequency typically results in field magnitudes of a few microTesla or less. The calibration factor is then necessarily assumed linear, even though the magnetic field of the primary experiment is several orders of magnitude larger than the field magnitude used to calibrate the probe. In this work calibration factors of two differential configuration magnetic field probes are presented as functions of frequency and field magnitude. Calibration factors are determined experimentally using a 80.4 mm radius Helmholtz coil in two separate configurations. A conventional low-magnitude calibration using a network analyzer with field magnitude of 158 nT yielded calibration factors of 15,107±233 and 4,899±180 T/V-s at 457 kHz for the surface mounted inductor and hand-wound probe, respectively. A relevant-magnitude calibration using a pulsed-power setup with field magnitude of 43.5 to 83.0 mT yielded calibration factors of 14,541±41.8 and 4,484±15.8 T/V-s at 457 kHz for the surface mounted inductor and hand-wound probe, respectively. The uncertainty reported is one standard deviation of the repeated calibration measurement. Low-magnitude calibration always resulted in a larger calibration factor, with a maximum difference of 18.5%. Comparison of the pulsed-power Helmholtz coil current waveform with the magnetic field waveform measured with the magnetic probes showed differences of 1.4% and 0.7% in the waveform extrema at 457 kHz for the surface mounted inductor and hand-wound probe, respectively.