A portable activity monitoring device comprising a housing having a physical size and shape that is adapted to couple to the user's body, a motion sensor to detect user motion and, in response thereto, to generate data which is representative of motion of the user, an altitude sensor to detect a change in user altitude and, in response thereto, to generate data which is representative of the change in altitude of the user, processing circuitry to calculate activity metrics of the user, wherein the processing circuitry: (i) calculates a motion metric using the motion data, (ii) calculates an altitude metric using the altitude data, and (iii) calculates at least one sleep metric of the user. In certain embodiments, the processing circuitry may automatically determine a sleep mode of the user using the motion data and calculate at least one user sleep metric.
