A system and method for determining head-disk contact (HDC) in a magnetic recording disk drive uses the signal from the magnetoresistive (MR) read head. The analog MR signal is digitized and input to a digital signal processor with circuitry and/or software for integrating the signal amplitude over a low-frequency range. The calculated value from the integration when the slider is out-of-contact with the disk is a reference value. The same integration is then performed during operation of the disk drive and the measured value is compared to the reference value. If the measured value exceeds the reference value by some predetermined amount, this is an indication of the onset of HDC or that HDC has occurred. The method can be used in head-disk testers to facilitate the design and testing of disk drive components, such as slider-suspension assemblies and fly-height actuators located on the slider to alter the head-disk spacing, and in disk drives to control fly-height actuators and to take corrective action prior to HDC.