It is shown that heat capacities of linear macromolecules consisting of all-carbon single-bonded backbones can be calculated from the appropriate contributions of substituted carbon atoms to a precision of about − 0.2±2.5% (155 data points), which is similar to the experimental precision. Heat capacity contributions of 42 groups are given over the full range of measurement and reasonable extrapolation. The quality of the addition scheme is tested on 16 series of measurements on homopolymers, copolymers and blends. The addition scheme works for all these different states of aggregation of the constituent groups. The basis of the addition scheme is discussed.