Features are disclosed relating to determining an activity in which a user is (or has been) engaged. One such activity is the taking of steps (e.g., walking or running). Some embodiments described herein are directed to accurate detection and counting of steps made by a user wearing a device with step-detection functionality. The accurate step counting can be facilitated by detecting signatures of certain activities, and determining whether to count steps based on an analysis of acceleration data over various intervals and moving windows of time.