Abstract This study investigates the ultimate shear strength of unstiffened slender web in prismatic tapered steel beams using newly proposed buckling coefficients raised in the preceding research conducted by the authors [1]. An experimental program is performed using three specimens that are selected to fail in shear without any significant flexural deformations. A three dimensional numerical finite element model is established considering both material and geometrical non-linearities. The finite element model is successfully calibrated to simulate the experimental tests. New procedures are proposed to predict the ultimate shear strength which is validated against the existing experimental results. The developed finite element models are used to expand the validation range of the proposed method to include the practical ranges within the relevant specifications limits.