Abstract: A computer-implemented method for estimating surface area and/or volume of a subject's body or body part. First, at least one image, including the subject's face, is obtained. The image is processed to determine facial image parameter(s) of the subject's face. The subject's characteristic(s) including age, weight, height, and/or gender—is/are also determined. A facial parametric model and the facial image parameters are used to determine facial shape parameters of the subject's face, where the facial parametric model relates specific values for facial image parameters to a respective 3D representation of a face having respective values for the facial shape parameters. A prediction model with the characteristic(s) and the facial shape parameters are used to predict a 3D representation of the subject's full body. The predicted 3D representation of the subject's full body is analyzed to estimate the surface area and/or volume of the subject's body or body part.