Asphaltenes are a class of molecules that are defined by the conditions of their insolubility in a particular solvent, such as heptane. A better understanding of the molecular properties of this mixture of molecules is needed in order to understand the mechanisms of coke and sludge formation during refinery upgrading operations. In this work we develop molecular representations for Ratawi and ANS asphaltenes using C-13 and H NMR techniques. These representations differ from the "average structures’ given previously in that a molecular weight is not assumed for the "average molecule". We show that these NMR techniques can be used to generate molecular representations that automatically provide estimates of the number average molecular weight and that these estimates are consistent with the upper bound on the number average molecular weight that was given previously for these asphaltenes. Both liquid- and solid-state techniques yield representations that display essentially equivalent molecular characteristics, although these techniques are essentially independent. The representations making use of liquid-state NMR require a portion of the proton spectrum to be consistent with a corresponding portion of the C-13 spectrum, while in the solid-state method, cross polarization and dipolar dephasing techniques are required to give self-consistent information. In both cases one makes use of the chemical relationship between the amount of bridgehead carbons and the size of certain polynuclear aromatics. The molecular equivalence of these representations suggests that the asphaltenic molecules are smaller than previously assumed and that the R groups attached to the polynuclear aromatic core are not as long as previously believed.