The present invention relates to a method for calculating the body condition score—BCS, the weight of an animal and its state of fertility by means of the mathematical processing of some characteristic morphological traits of the observed subject, which makes use of at least one contact or no-contact detection device of the profile 109 of the animal, at least a data processing unit and a program that implements a specific mathematical method of interpretation. By such a method, the determination of the body condition and its synthetic index or fattening index or FI, is independent of species, race, gender, age and absolute size of the examined animal. This method is also robust to possible errors of positioning of the apparatus by an operator.