Dimensional weight is a calculation of a theoretical weight of a package. This theoretical weight is the weight of the package at a minimum density chosen by the freight carrier. If the package is below this minimum density, then the actual weight is irrelevant as the freight carrier will charge for the volume of the package as if it were of the chosen density (what the package would weigh at the minimum density). Furthermore, the volume used to calculate the dimensional weight may not be absolutely representative of the true volume of the package. The freight carrier will measure the longest dimension in each of the three axis (X, Y, Z) and use these measurements to determine the package volume. If the package is a right-angled rectangular box (cuboid), then this will be equal to the true volume of the package. However, if the package is of any other shape, then the calculation of volume will be more than the true volume of the package.