Skin graft harvesting systems and methods based on impedance monitoring are disclosed that utilize impedance sensors to automate the harvesting of skin grafts or assist a user in deciding when the skin graft is ready to be harvested. Such systems and methods can reduce the burden of visual observation and ensure greater reliability and consistency of the grafts. The systems, methods, and devices disclosed herein are particularly useful with harvesters that rely upon suction and/or heating to raise a plurality of small or “micro” blisters simultaneously.