Technical Abstract: Young's modulus is a measure of a material’s resistance to deformation as the material is forced to elongate. Modulus values for cotton can be determined by performing tension tests experiments on cotton fibers or, as in this study, by stretching molecular models in a computer program. However, reported experimental and calculated values show large ranges. Herein we present a series of modulus estimations that used computer programs with molecular mechanics (MM) and quantum mechanics (QM) functions. Calculations were performed on a series of short cellulose Iß models, the more abundant form of cellulose found in cotton fibers. Computer -based computations with a short (2 sugar units) cellulose model and an analogue incapable of making hydrogen bonds revealed a considerable contribution of intramolecular forces to the modulus of cellulose. Calculations with longer cellulose chains models (10 sugar units) resulted in a modulus value comparable to reported values for cellulose crystals.