Abstract: A sizing device or gauge is provided for measuring whether an article such as a package for delivery has dimensions that lie within predetermined values of length, width and volume. The sizing device is formed by a receptacle that has a flat rectangular base wall which defines predetermined maximum values of length and width for the item, and a pair of adjacent upstanding side walls portions of which decrease in height away from adjoining ends of the walls, the height decrease being in inverse relation to the square of a respective one of the maximum height and width values. The device is useful for example in determining whether items meet the specifications of a delivery service segregating items into different categories.