Nuclear magnetic resonance (NMR) has become a well-established method to characterize the structures of biomolecules in solution. High-quality structures are now produced, thanks to both experimental and computational developments, allowing the use of new NMR parameters and improved protocols and force fields in structure calculation and refinement. In this chapter, we give a short overview of the various types of NMR data that can provide structural information, and then focus on the structure calculation methodology itself. We discuss and illustrate with tutorial examples both "classical" structure calculation and refinement approaches as well as more recently developed protocols for modeling biomolecular complexes.