X-ray diffraction with the assumption of uniform stress has been used for determining the crystal modulus of polymers. Values of the modulus of silk obtained previously using such an approach were found to be an order of magnitude lower than, those obtained by computational modeling. The differences are outside the limits of experimental and computational errors. This study re-examined the values in an improved manner. For the X-ray technique, moduli of different samples along the length of cocoon fibers were measured. The values obtained are 20-28 GPa depending on the crystallinity index and degree of orientation of the samples. For the computational calculation, the longitudinal acoustic mode (LAM) frequency of silk systems having three different c-axis dimensions were calculated. An acoustic dispersion curve was generated from the frequency values. The slope of the curve at the origin gave a crystal modulus of 13 GPa. A 3D-fluctuation analysis yielded an average modulus of approximately 16 GPa. These low values result from the out-of-plane torsioning of molecules in the P-pleated structure of the silk crystals. The experimental and computational results are in reasonable agreement with one another as well as with data reported in the literature for other pleated molecules.