Image by Ian Simmonds for Unsplash

Given how important tonnage is in the world of shipping, we put together a ready to use tonnage calculator—or, more precisely, two of them. These tonnage calculators will allow you to estimate the average gross and net tonnage of a vessel—later in this article, we look into what gross and net tonnage actually mean in case you want further clarification.

For gross tonnage, we require you to input the total enclosed volume of the vessel in cubic meters (including non-commercial spaces such as engine rooms or living quarters).

For net tonnage, on the contrary, we require you to input the TEU capacity of a vessel—namely, how many containers a vessel can carry at a time. 

Cubic Meters to Gross Tonnage Converter

Calculate Gross Tonnage

TEU to Gross Tonnage Calculator

Calculate Gross Tonnage

Note: The actual tonnage of a vessel might vary considerably given its dimensions. We use a standard formula to calculate tonnage—and outline its elements below.

What Is Tonnage?

The term tonnage refers to the total volume of cargo a ship is able to carry at any given point. This doesn’t mean that a ship will always travel with cargo equal to its tonnage. In fact, given the dimensions of the vessel and the inability to cover the total space of a ship, there will always be some space left unused.

Tonnage is also referred to as the carrying capacity of a vessel since, as the name suggests, the term includes the total amount of cargo a vessel could carry to import or export. Needless to say, it is a crucial concept for maritime logistics.

What Is Gross Tonnage?

Gross tonnage refers to the total tonnage of a vessel, including any additional rooms or compartments that could be used to carry non-commercial goods and are enclosed within the vessel. Meaning, sleeping quarters, administrative rooms, or any other space within the vessel itself. So, it is the total carrying capacity of a vessel.

What Is Net Tonnage?

Net tonnage refers to the commercial space occupied within a vessel. That is, the total volume of commercial cargo a vessel is able to carry at any given time. As you can see, Net tonnage can be thought of as a subset of gross tonnage, or, the equivalent of subtracting all non-commercial areas from the gross tonnage of a vessel.

How to Calculate Tonnage?

While the actual tonnage of a vessel might change according to its actual dimensions, you can easily find it using a simple formula. The Gross Tonnage of a Vessel is defined as the product of the volume of its enclosed spaces times a constant K1. That is:

GT = K1*V

K1, in turn, represents the product of 0.02 times the base ten logarithm of the vessel’s volume plus 0.2. Or, as shown below:

K1 = 0.2 + 0.02* log10 (V)

This is the formula we use above to calculate the gross and net tonnage of a vessel in our tonnage calculator.

Why Is Tonnage Important in Shipping?

You might not think much of tonnage when you have other units to measure the volume of a vessel readily available such as TEUs or metric tons. However, tonnage is often used to estimate the costs of entering a port or crossing crucial trade choke points such as the Panama Canal or the Suez Canal. So, if you are looking to dock at a port, there is a high chance that your vessel’s tonnage will be used to determine the fees you must pay.