1kg of cotton and 1kg of iron – which is heavier?

Some people enjoy asking questions like this. You might have seen people discussing it from the point of view of physics. However, I am seriously asking you: “Which is heavier, 1kg or cotton or 1kg of iron?” Why am I asking this? The reason is that, when one is transporting cargo as airfreight, 1kg of cotton is considered heavier than 1kg of iron. How could that be?

The actual weights are the same; however, when the air cargo/airline industry calculates air freight charges, the volume of cargo is converted to theoretical weight. This makes a shipment of light weight density theoretically “heavy,” so to speak. Therefore, cotton is “heavier” in terms of calculating freight charges because it takes up more space than iron does.

Airlines use a certain formula to convert volume to weight. The theoretical weight calculated this way is called “volumetric weight” or “dimensional weight”. The higher of the actual gross weight or the volumetric weight will be the chargeable weight used to calculate the air freight charges.

How do you calculate the volumetric weight?

The airfreight volumetric weight is a theoretical weight based on the length, width, and height of a package. The volumetric weight formula is:

Length (cm) x Width (cm) x Height (cm) ÷ 6,000

Why do airlines use volumetric weight instead of charging based solely on the actual weight?

Cotton and steel example:

Let’s see what would happen if airlines charged based solely on weight.

Take an aircraft with an available space of 10 cubic meters. A shipper sends a shipment of steel that occupies 10 cubic meters of space, and the shipment weighs 77,000kg. If the air rate is Y1,000 per kg, the airline will receive the amount of Y77,000,000 as freight charges. If another shipper sends a shipment of cotton that takes up 10 cubic meters, the weight may be 800kgs and the airline would receive only Y800,000, which is much less than the freight charges for a steel shipment, even though the cotton shipment takes up the same space. An aircraft has limited space, and space is important to airlines. Thus, they adopted the concept of volumetric weight to receive a reasonable fee even when they are transporting cargoes that is low in weight density. This is a standard set by the International Air Transport Association.

Example:

A box with dimensions of 1m x 1m x 1m (100cm x 100cm x 100cm).

The volumetric weight of this box is 100 x 100 x 100 x 100 ÷ 6000 = 166.6666kgs (rounded up to 167kgs). If this package weighs 200kgs, the chargeable weight will be 200kgs. If it weighs only 150kgs, the volumetric weight will apply and the chargeable weight will be 167kgs, as 167 is larger than 150.

Courier companies such as DHL and UPS use a different formula, which is Length (cm) x Width (cm) x Height (cm) ÷ __5,000__. This makes the chargeable weight of shipments of low weight higher if the items are shipped by courier companies, e.g., the chargeable weight of the above-mentioned 100m x 100cm x 100cm box will be 200kgs when shipped by courier.

Summary:

When shipping by air, both the volume and the weight are pricing factors.

The theoretical weight converted from volume is called “volumetric weight”.

The volume is converted to weight using a certain formula: Length (cm) x Width (cm) x Height (cm) ÷6,000.

The higher of the actual gross weight or the volumetric weight is the chargeable weight.

When a shipment’s weight density is comparatively low, the volumetric weight is likely to apply.