What Is CBM, And How Do You Calculate It?

When you ship goods from one country to another through sea, road, or air, the term 'CBM' often comes up. CBM for cubic meters is a unit of measurement that determines how much the shipping would cost. 

Therefore, when you offer worldwide shipping on your ecommerce store, you must understand everything there is to know about CBM. In this guide, we'll explain CBM and how to calculate it. 

What Is CBM? 

CBM is a unit of measurement that is used to calculate the shipping cost of goods. Since it represents cubic meters, it shows how much space an item will take on a truck, aircraft, or ship, depending on the shipping vehicle. In cargo transport, the amount of space a package takes determines its cost of transport. 

How Do You Calculate CBM?
To calculate CBM, you'll need to know your package's length, width, and height in meters. Then, simply multiply these three measurements together to get your CBM calculation.
Do note that this method only works for cargo shaped like a cube or cuboid. Since these are regular shapes, they have uniform dimensions and can be easily measured. If your package is not in one of these shapes, you'll have to use different formulas, depending on the shape of the package. 

The formula for measuring CBM of a cube or cuboid shaped carton is:
Length x width x height
When using this formula, make sure all measurements are in meters. If they are in other measurement units, convert them to meters. 

Suppose a carton is 3 meters wide, 3 meters long, and 3 meters high. You'll simply put these figures in the formula enough. The CBM of your package will be 27m³. 

The ''3'' in the superscript of the unit of measurement indicates that there were three measurements. Now, if you have 20 or 50 cartons of the same size, you can multiply 27 by 20 or 50 respectively to get the CBM of your total cargo.

But if your cargo contains cartons of different sizes, you can calculate CBM for them individually. In the end, you have to add the CBM for each carton to get the final CBM for the whole cargo.

CBM Of A Cylindrical Carton 

If your cargo is shaped like a cylinder, you won't be able to calculate its CBM using the formula above. Instead, you'll have to use a different formula:
CBM = π x height x radius²
π refers to pie. Its value is 3.14, which means you will multiply the height and radius of the cylindrical carton by 3.14. The ''radius'' in this equation is half of the diameter of the cylinder. The diameter is the distance from one side of the circle to another measured through the center.
Suppose you have a cylindrical carton that is 15 meters high and has a diameter of 10 meters.

The radius will be 5 meters (10/2). Plugging these values in the equation above, we get: 

CBM = 3.14 x 15 x 5²
CBM = 1,177.5 m³ 

Again, if you have a number of cylindrical cartons of the same size, you can multiply 1,177.5 by the number of cartons to get the CBM for your total cargo. But if your cargo consists of cylindrical cartons of different sizes, you'll have to calculate the CBM for each one and add them up.

CBM Of An Irregularly Shaped Package
When you have an irregularly shaped package, you can't use any of the aforementioned formulas to calculate its CBM. The best option in this regard is to measure the longest length, the widest width, and the highest height of the package.

Multiply these values to get the CBM of the package. Again, you need to make sure all values are in meters to keep your calculations correct and uniform. If the measurements are in feet, you can convert them to meters by multiplying with 0.305.

Likewise, you can convert inches to meters by multiplying with 0.025. For centimeters, multiply the value by 0.01 to get the answer in meters. 

Using CBM to Calculate Freight
You can use CBM to calculate freight for air, ship, or road transport. For all methods, the transport companies charge the customer based on whichever of the two weights - dimensional or gross - is greater in value.

The package's dimensions are taken in cm for air and road freight. For ocean freight, convert the values to meters. Here are the methods for all three modes of transportation.

Ocean Freight
Suppose you want to send an LCL (less than a container load) shipment by sea and all three dimensions of your package are 5 meters. The CBM will be 125m³.

The dimensional weight of the package will be measured using the DIM factor, a mathematical value that indicates the volume of a carton per unit of its weight. The DIM factor, in this example, is 1:1000, and the gross weight of the carton is 200kg.

Typically, shipping lines only charge freight based on weight when the cargo weighs more than 1 ton. The cargo weighs 0.2 tons in this example, so the freight is calculated based on CBM.
Let's say the ocean carrier charges $100 per CBM/ton. The freight cost will be 100 x 125 = $12,500. Meanwhile, if the gross weight of the package was 5,000 kg or 5 tons, the freight will be calculated based on the weight and not the CBM. In that case, the freight will be 100 x 5 = $500.

Air Freight
For air freight, the dimensional weight is calculated by dividing the CBM with the DIM factor, where the DIM factor is 1:6000. Let's say that all three of the package dimensions are 200cm, and the gross weight is 200kg.

The dimensional weight will be calculated by:
200 x 200 x 200 / 6000 = 1,333kg (1.3ton)

Since the dimensional weight is greater than the gross weight, the ocean carrier will charge the customer according to this. Assuming the ocean carrier charges $100 per ton, the freight cost will be 1.3 x 100 = $120.

Road Freight
The same formula is used for road freight except that the DIM factor is 1:3000. Suppose the package dimensions are 100cm, 80cm, and 50cm. The dimensional weight will be:
100 x 80 x 50 / 3000 = 133kg or 0.13 ton

Let's say the gross weight of the package is 100kg or 0.1 tons. Since the dimensional weight is larger, the freight will be calculated using its value. Assuming the per ton charges for air freight are $100, the freight cost of this package will be 0.13 x 100= $13.3. If the gross weight was larger, such as 200kg or 0.2 tons, the freight cost would be $20. 

Which Factors Influence CBM Rates?
Now that you know about different methods of CBM calculation, it's also important to learn about the factors that affect the CBM rate transport companies charge to customers. Some of these factors are discussed below. 

Handling Charges

The handling charges differ from one port to another. These are the charges port authorities take for certain services, equipment, and facilities. They also cover the offloading and loading of the cargo. 

Currency Adjustment Factor

The currency adjustment factor is determined by the exchange rate between the currency of the destination port and the currency of the shipping port. It's used to adjust the cost of transport services to reflect fluctuations in currency rates. 

If a customer frequently uses a port of the transport company, they may get preferential rates. Typically, frozen cargo is easier to handle, whereas dry cargo's handling is more complicated. For the latter, the currency adjustment factor will also reflect the costs for additional processes needed to manage the cargo. 

Bunker Surcharge or Adjustment Factor
The bunker adjustment factor is determined by the price of fuel. The factor is used to account for the increased cost of fuel and its effects on transport services. 

Final Words

By now, you should know how to calculate CBM for different types of packages and determine the freight charges accordingly. It's important to research the rates of different companies before making a decision. By doing some calculations beforehand, you can save a significant amount of money on your shipping.