The degree of asphaltene aggregation (Dagg) over a wide range of concentrations in various solvents under ambient conditions was examined using a quantitative index derived from Rayleigh scattering measurements by ultraviolet–visible spectrometry and the Hansen solubility parameter (HSP). The source of asphaltene was Canadian oil sand bitumen. The target concentration was ≤10%, and the source of the solvent was organic solvents having Δδ ≤ 5.5 MPa0.5 of the HSP distance between each solvent and the asphaltene, such as toluene (TL), bromobenzene (BB), and toluene–pentane (TL–PT), toluene–bromobenzene (TL–BB), and toluene–quinoline (TL–QL) mixed solvents. Through these measurements, the effects of the concentration and solvent on Dagg were examined quantitatively, which enabled the mapping of Dagg. The Dagg map obtained facilitates estimation of Dagg under desired conditions, understanding of asphaltene aggregation behavior, and creation of a reasonable aggregation model.