AbstractThe swelling of microcrystalline, native and mercerized cotton and eucalyptus celluloses by 16 aprotic solvents was investigated. The number of moles of solvent/anhydroglucose unit, nSw, correlates well with solvent molar volume, basicity and dipolarity/polarizability. Swelling is sensitive to cellulose crystallite size, surface area and the presence of its chains in parallel or anti‐parallel arrangements. Use of solvatochromic parameters is a superior alternative to the use of other descriptors, such as Hildebrand's solubility parameters and Gutmann's donor numbers. The calculated nSw for 28 protic and aprotic solvents correlated well with their experimental counterparts, although hydrogen bond donation by the solvent was not included.magnified image