An electronic device may include a motion sensor for detecting movement of the electronic device and a pressure sensor for detecting changes in elevation of the electronic device. Applications that run on the electronic device such as health and fitness applications may use motion sensor and pressure sensor data to track a user's physical activity. For example, processing circuitry in the electronic device may use the motion sensor to track a user's steps and the pressure sensor to track changes in the user's elevation. The processing circuitry may determine whether the user is climbing stairs based on the user's step rate and the user's changes in elevation. When the processing circuitry determines that the user is climbing stairs, the processing circuitry may use the pressure sensor and motion sensor to track and store the number of flights of stairs climbed by the user.