CBM (Cubic Meter)

In international trade, logistics and freight forwarding, the cubic meter (CBM) is an internationally recognized unit of measurement for cargo volume, widely used in domestic and international transportation. Knowing and calculating the cubic meter volume of cargo is essential for planning transportation, booking space, managing inventory and estimating logistics costs. So, how is the cubic meter calculated? What are the key factors in calculating the cubic meter? This article will explain in detail.

Basic definition of CBM

CBM is an abbreviation for Cubic Meter, which can also be expressed as m³. It is an internationally standardized unit of volume measurement used to measure the amount of space goods take up during transportation or storage. Put, 1 CBM is the volume occupied by a cube with sides of 1 meter each (1m x 1m x 1m = 1 m³). CBM is the universal language used to measure the “size” of goods in international transport (especially Ocean Freight and Air Freight) and warehousing industries.

How is CBM calculated?

Calculation rules: The CBM of goods in a square or rectangular box shape is very straightforward. The basic formula is as follows:

CBM = length (L) × width (W) × height (H)

When using this formula, please note the following:

• Unified units: All measurements of length, width and height must be in units of “meters (m)”. If your measurements are in centimetres (cm), you need to convert each dimension to meters by dividing it by 100 and then multiplying. For example, the CBM of a box measuring 50cm x 40cm x 30cm is calculated as follows: 0.5m × 0.4m × 0.3m = 0.06 CBM.
• Multiple items: If you have multiple items of the same size, calculate the CBM of a single item and multiply it by the total number of items to get the total volume. If the items are different sizes, calculate the CBM of each item separately and add them up.

Why is CBM important for calculating freight?

CBM is important because it directly affects freight calculation, especially in Ocean Freight (LCL) and Air Freight. The freight company (whether it is a shipping company or an airline) usually charges based on the actual weight (Actual Weight) or volumetric weight (Volumetric Weight) of the goods, and the greater of the two is used as the chargeable weight (Chargeable Weight).

• Volumetric Weight: This concept is designed to balance out the valuable transport space taken up by “lighter goods” (i.e., light but bulky goods). CBM is the basis for calculating volumetric weight. The shipping company converts the goods’ CBM into volumetric weight (usually in kilograms kg) using a specific conversion factor (special rules for Air Freight will be mentioned later).
• Billing weight: If a shipment’s volume weight is greater than its actual weight, the freight is calculated based on the volume weight. Conversely, if the actual weight is greater (commonly called “heavy cargo”), the actual weight is charged.

Therefore, calculating CBM is the first step to obtaining an accurate freight quote and controlling logistics costs. It determines how much “expensive” space your goods occupy in a container, aeroplane cargo hold, or truck.

Precautions when measuring and calculating the CBM of goods

To ensure the accuracy of the CBM calculation and avoid subsequent hassle and additional costs, please note the following:

• Measure the outer packaging: Always measure the outermost dimensions of the packaged goods, including any protruding parts.
• Measure accurately: Measure the length, width and height as accurately as possible. Small errors can become significant when multiple items are added together.
• Units consistent: Once again, ensure all units have been converted to “meters” before calculating.
• Consider pallets: If the goods are transported on a pallet, the dimensions of the pallet (length, width, height) usually need to be included in the measurement.

Special rules for calculating CBM for Air Freight

Although CBM is a volume unit, the conversion rules for calculating “volume weight” for Air Freight are usually different from those for Ocean Freight. Space is more limited, and costs are higher for Air Freight, so the volume-weight conversion factor is usually more “sensitive” for lightweight goods.

• Standard Air Freight volume weight factor: The commonly used volume weight conversion formula for international air freight is:
  • CBM (kg) = (length cm × width cm × height cm) / 6000
  • or, equivalently: CBM (kg) = CBM × 167
  • This means that 1 CBM is equivalent to 167 kg for Air Freight.
• Express delivery and regional differences: It is worth noting that international express delivery companies (such as DHL, FedEx, and UPS) may use a different divisor, most commonly 5000. That is:
  • Volumetric weight (kg) = (length cm × width cm × height cm) / 5000
  • Or, equivalently: Volume Weight (kg) = CBM × 200
  • This means that 1 CBM may equal 200 kg for express delivery channels.

Important: When calculating the volume weight for Air Freight, always check with your airline or freight forwarder which specific conversion factor they use (whether it is divided by 6000, 5000, or some other value).

How is the CBM of an irregularly shaped package calculated?

For goods with non-standard cubic shapes (such as cylinders, tubes or irregularly shaped items), an estimation method is used to calculate the CBM. The standard practice in the industry is as follows:

• Measure the largest dimension: Find the point on the item that projects the most in the three dimensions (length, width and height).
• Construct a virtual cube: Imagine a rectangular box that is as small as possible and can hold an irregular item.
• Calculate the CBM of the dummy cube: Using the measured maximum length, width and maximum height, calculate the CBM of this dummy cube using the standard formula (L_max × W_max × H_max).

For a cylinder, for example, the “length” may be the height of the cylinder, and the “width” and “height” may be its diameter. Even if the actual space occupied is less than this virtual cube, the carrier will usually calculate the CBM and the corresponding volume weight based on these maximum external dimensions, as this is the regular space it occupies in the transport vehicle.

How many cubic meters does a container hold?

Containers have a limited CBM capacity. Knowing the internal volume of a standard container is important for planning full container load (FCL) transport. The following are the theoretical internal volumes (approximate values) of some common containers:

• 20ft container (20′ GP): approx. 33 m³
• 40ft container (40′ GP): approx. 67 m³
• 40′ High Cube (40′ HQ): approx. 76 m³

Please note: This is the maximum theoretical internal volume. During the actual loading process (“stuffing” or “crating”), the actual loadable CBM is usually significantly lower than the theoretical value due to the following factors:

• Cargo shape and packaging: not all goods can be stacked perfectly, creating gaps.
• Loading and unloading space: operating space needs to be allowed.
• Fixing and bracing: Dunnage and securing devices also take up space.
• Weight limits: Containers have a maximum weight limit; even if the space is not fully occupied, it cannot be loaded any further when the weight limit is reached.

Generally speaking, the actual usable loading volume of a 20’GP may be around 25-28 m³, while the actual usable volume of a 40’GP and 40’HQ is around 54-58m³ and 60-68 m³ respectively. The exact values depend on the specific circumstances of the goods and the packing technique.

Conclusion

CBM (cubic meter) is the basic unit of measurement for the volumetric capacity of goods in international logistics and transportation. Accurate understanding and calculation of CBM is essential for determining the mode of transportation, estimating and controlling freight rates, optimizing the utilization of container or cargo space, and efficiently managing storage. Whether it is a regular or irregularly shaped cargo, knowing how to calculate CBM and its application rules in different transportation scenarios is essential for anyone involved in global transportation.