There may be some complicated physics formulas to estimate the amount of weight that a cabinet drawer can support. Generally, though, a guesstimate will be sufficient. The weight load of a drawer will depend upon the materials used in its construction. It will also depend upon the thickness of the materials used. For example, a solid oak drawer will be capable of bearing more weight that a drawer constructed of pine in the same thickness. The joining method needs to be taken into consideration as well. Traditional dovetails and biscuit or rabbet joints will be able to support more weight than a drawer joined with bolts or other metal fasteners.