We describe sensitive magnetometry using lumped-element resonators fabricated from a supercon- ducting thin film of NbTiN. Taking advantage of the large kinetic inductance of the superconduc- tor, we demonstrate a continuous resonance frequency shift of 27MHz for a change in the magnetic field of 1.8lT within a perpendicular background field of 60mT. By using phase- sensitive readout of microwaves transmitted through the sensors, we measure phase shifts in real time with a sensitivity of 1􏰀/nT. We present measurements of the noise spectral density of the sen- sors and find that their field sensitivity is at least within one to two orders of magnitude of super- conducting quantum interference devices operating with zero background field. Our superconducting kinetic inductance field-frequency sensors enable real-time magnetometry in the presence of moderate perpendicular background fields up to at least 0.2 T. Applications for our sen- sors include the stabilization of magnetic fields in long coherence electron spin resonance measure- ments and quantum computation.