1.1 Overview and why is it necessary to calculate the chargeable weight?

You may notice that the 02 columns are related to weight on the air waybill: Gross weight and Chargeable weight. Due to freight calculation, Gross weight is the actual weight and the Chargeable weight may be equal to or greater than the actual weight (Gross weight).

That is to say, some small but heavy items will cause loads to reach weight thresholds before the cargo hold is actually filled up. On the contrary, light but bulky items will take up space in the aircraft and fill up the cargo hold before reaching the payload threshold.

Therefore, IATA (The International Air Transport Association) has issued a regulation on the general rules and methods when calculating the chargeable weight for freight services. Accordingly, heavy goods will be calculated according to the actual weight (Gross weight) and bulky goods will be calculated according to the volumetric weight (Volume weight).

1.2 Steps to calculate the international shipping fee

Step 1. Scale the actual weight

Use the scale to determine the weight of the package. Round the weight to the next half a kilogram.

Step 2. Calculate volumetric weight

Calculate the volume by multiplying the length by width and height (each dimension is rounded to the nearest centimeter).

Volumetric weight

L = length in centimeters

W = width in centimeters

H = height in centimeters

(L x W x H)/5000=Volume Weight (kg)

Weight will be rounded to the nearest 0.5 
Every package needs to be packed with shrink film, pallets to strengthen and secure the goods during international shipping. Therefore, the actual weight that a carrier like Janbox Express charges will be higher than the total weight of the packages. For that reason, the billable weight of each package will be rounded up to 0.5 to make up for this cost deficit during transportation.
Moreover, it is regulated by IATA and is generally applied to international carriers.