Approaches to enable a computing device, such as a phone or tablet computer, to determine depth information about an object captured by a single camera of the device without requiring multiple cameras to capture that object in their field of view. For example, the computing device may track the object throughout a sequence of images using a single rear-facing camera and then determine the depth information of that object by combining data about the object's changes in size (throughout the sequence of images) and information about the distance between the computing device and a user's face (or other user's feature) that can be determined using two or more front-facing cameras configured for stereo imaging. The depth information of the object may include the distance between the computing device and the object, the distance between the object and the user's face, or the physical dimensions of the object, among other such information.