In the case of a single compound in solution the area of NMR signals is proportional to the number of equivalent protons that resonate at each chemical shift, regardless of the multiplicity of signals. Integration is therefore very important information for determining or confirming a molecular structure.
On a spectrum, integration is relative and is given by the height of the integral curve of the signals.

In the case of a mixture of compounds, it is thus possible to know the relative proportion of the components of the mixture. Studies of the progress of reactions or the composition of mixtures are therefore possible by NMR.