How do I calculate the volume of a parcel with unequal sides? In this case, the longest dimensions (length x width x height) are used to calculate the volume (dm3). Gerelateerde vragen What are the maximum dimensions of a package? How much does the 'signature on delivery' shipping option cost in Belgium? My parcel is within 50dm3. Is a surcharge applied anyway? What does 1dm3 mean? What is the maximum allowed weight of a return parcel?