Method for determining buoyant mass and deformability of a cell. The method includes introducing the cell into a suspended microchannel resonator that includes a constriction near a distal location in the resonator. A first frequency shift in the resonator is monitored as a cell moves to the distal location in the resonator, the first frequency shift being related to the buoyant mass of the cell. Transit time of the cell through the constriction is measured by monitoring a second frequency shift as a result of a change in cell location as it passes through the constriction, whereby deformability is determined from the measured buoyant mass and transit time.