Recent studies on heat capacity calorimetry of nanomagnets including single-molecule magnets are reviewed. Single-molecule magnet is the name of paramagnetic molecules showing superparamagnetic behavior and blocking of magnetization reversal despite the absence of magnetic long-range order. Heat capacity calorimetry plays an important role in the characterization of this class of nanomagnets, not only for determination of spin energy levels and magnetic anisotropy but also for confirming the absence of magnetic long-range order. In another view, single-molecule magnets serve as a playground for the demonstration of kinetic selection rule dominating thermal excitations, thanks to an additional control parameter of external magnetic field which can open/close relaxation channels relating to transverse or longitudinal manner of application. Related nanomagnets covering single-chain magnets and antiferromagnetic spin rings are also discussed. The Zeeman-split spin levels of the latter show avoided crossings due to the off-diagonal matrix elements of magnetic anisotropy, and it is revealed that heat capacity calorimetry is useful for understanding such level systems.