What is volumetric weight?
For postal services like Royal Mail, shipping cost is based on weight. However, the courier's shipping fees are calculated on the amount of space that your shipment occupies in transit rather than the actual weight, this is called the volumetric weight. This is an industry-standard. The actual weight would only be charged when it is higher than the volumetric weight. You can calculate volumetric weight using the formula: Length * width * height (cm) / 5000. See below for examples.
For example, if a parcel weighs 1 kg, 30 x 30 x 30 cm, the volumetric weight is 5.5 kg. Since the volumetric weight is higher than the actual weight of 1 kg, Couriers DHL and UPS will therefore use 5.5 kg for the shipping rates. It depends on the Carrier, so it is beneficial to reduce parcel volume to save on shipping costs.
Volumetric weight is calculated using the following formulas:
In the Metric unit, Length (cm) x Width (cm) x Height (cm) / 5000. For example, 35 cm x 24 cm x 29 cm / 5000 = 4.87 Kg.
In Imperial unit, Length (in) x Width (in) x Height (in) / 139. For example, 21 in x 17 in x 14 in / 139 = 35.96 lbs