The frequencies of the fundamental and second modes of lateral vibration of a cantilever beam under the action of its own weight are determined approximately by using the Galerkin method. The corrected formulas for calculating the Young's modulus of the beam material are derived from these solutions. The experimental results for the fundamental mode of vibration of cantilevers are presented. It is shown that Young's modulus of the material can be obtained exactly by treating the experimental data with the corrected equation. An expedient to foreknow the amount of the effect of weight on the given specimen is proposed.