The drapability of a textile composite reinforcement is its capability to be formed on a double curved shape without wrinkling. This is an important property of a textile reinforcement when it is used to manufacture a preform in liquid composite molding processes. The analysis of the deformation modes and the form of the internal virtual works during draping of a fibrous reinforcement leads to define a physics-based Drapability Ratio determined by the in-plane shear stiffness and the bending stiffness of the textile reinforcement. This Drapability Ratio can be used to identify the reinforcement that can be draped for a given geometry. Square box forming and cylindrical forming carried out for a set of textile reinforcements under the same conditions show the relevance of this Drapability Ratio.