The simple beam theory can predict the deflection of the loaded end of cantilever beams with a high level of accuracy if the length-to-diameter ratios for the beams are high. Hence the readily available formula (which is based on the simple beam theory) for cantilever beams may be used with confidence when the length-to-diameter ratios for the beams are high. However, studies on the accuracy of the results predicted by the simple beam theory are not common when the length-to-diameter ratios are small, especially when the Young's modulus is low. Hence the present work compares the results obtained through the use of the well-known formula (based on the simple bending theory) with the results obtained by making use of the well-known commercial finite element software ANSYS, for cantilever beams of different length-to-diameter ratios, in order to get an idea of the accuracy of the results that are obtained by making use of the well-known formula. The effect of Young's modulus is also looked into, by solving the same problems but for different Young's moduli. All these results are tabulated. The present study would be of use to designers who are concerned over the accuracy of the results that are obtained through the use of the well-known analytical formula.