This chapter addresses the importance of evaluating body composition, especially in the sports and health fields. Various models for estimating body composition are presented, highlighting the tissue model as one of the most utilized, as it allows differentiating between specific tissues such as adipose, bone, and muscle. The text also points out a common terminological error in the field of body composition, where the term ‘fat mass’ is generically used, although in reality other components such as lipid mass or adipose tissue are being estimated. This leads to confusion and to considering different concepts as synonyms when they are not. Following this, the chapter analyses different methods for estimating body composition, such as dual-energy X-ray absorptiometry (DXA or DEXA), hydrodensitometry or hydrostatic weighing (UWW), air displacement plethysmography (ADP), electrical bioimpedance or anthropometry, with an analysis conducted on their advantages and disadvantages. Subsequently, the estimation of body composition from anthropometry as an indirect or double indirect method, depending on how it is approached, is addressed. Bicompartmental, tetracompartmental, and pentacompartmental models are detailed for estimating body composition through anthropometric measurements, providing the equations recommended for use in each context. Finally, the use of the sum of skinfolds and corrected girths as alternatives for evaluating body composition is discussed, highlighting their usefulness in relation to adiposity and muscle development.