Rats have been used in experiments since before Christ and, currently, are the most commonly used animal in scientific research. The literature regarding the heart of these animals is not very detailed and descriptive. The few references that were found are old and detail only one aspect of the heart anatomy of these animals. The objective of this research is to study two macroscopic parameters that are yet to be described regarding the heart of Wistar rats in different phases of their lives. Thirty-six adult male and female rats (Rattus norvegicus) weighing 150-770 g were randomly set into 6 experimental groups according to gender and weight. After the excision, each heart was then carefully dissected and removed from the chest. After this process, each heart had their weight measured on a HELMAC HM100 precision scale, and the parameters tape-measured. Once rectified, this tape-measurement allowed the measurement of structures in a single n-dimensional level through an analog precision caliper. The measurements correspond to the perimeter of the atrioventricular groove (PAV) and the distance from the atrioventricular groove to the apex of the heart (DGA). Both these parameters are part of the surface anatomy of the heart and can help to understand the sexual dimorphism and the adaptation that occurs inside the heart when these animals gain weight.