ISO container: Definition, container sizes, types, and tracking software used in shipping

A complete guide to ISO containers and tracking tools


An ISO container is a large metal box, in the shape of a rectangular parallelepiped, designed and used to transport goods from one port to another by road, rail, sea, or air.

Today, intermodal containers are ubiquitous, and it’s easy to overlook how much they have transformed international trade. Since intermodal containers were introduced, they've become a key part of logistics, and it’s worth exploring facts about intermodal containers a little more.

Here are answers to the questions you didn’t know you had about intermodal containers, and a list of the best tools for tracking intermodal shipments:

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What is an ISO container?

An ISO container is:

  • a large metal box (made from steel, aluminium...) used to transport goods and manufactured products, adapted to several modes of transport;
  • an intermodal freight transport unit: A forty-foot container is regarded as two twenty-foot containers or 2 TEU (Twenty-Foot Equivalent Unit);
  • a container whose contents are not loaded or unloaded when the container is moved from one means of transport to another;
  • a container that meets the international ISO standards;
  • an experiment carried out successfully and democratised by the American businessman Malcolm Maclean, that supplied American soldiers with equipment in the 1940s;
  • a transport solution that allowed the development of international trade by sea.

There are two standard types of ISO containers: the 20-foot container and the 40-foot container. They are widely used in shipping, and are different from other types of containers because they are completely airtight.

Each type of intermodal container has specific dimensions (height, weight, length and, payload).

Here is a short video that explains the history behind containers:

Industry terms 101

Intermodal transportation

Intermodal transportation is when cargo is transported from one location to another by using several modes of transport.

When using intermodal transportation, each part of a shipment is handled by different shipping companies. This means that you will have several contracts, one with each shipping company to handle their specific part of the shipment.

What are the benefits of using intermodal transportation?

  1. Reduce costs. Because you handpick a carrier for each step of the shipment, you can take advantage of lower rates, and reduce handling costs.
  2. Environmentally friendly. By using intermodal transportation, you can choose environmentally-friendly shipping alternatives.
  3. Reliability, capacity, and safety advantages. Shippers have more access to equipment and standardized transit schedules. You can create partnerships with them and streamline reverse logistics.

Multimodal transport

Just like intermodal transportation, multimodal transportation is when cargo is transported from one location to another by using multiple modes of transport.

However, there is only one contract or bill of lading. Therefore, the same transport carrier is responsible for moving the entire shipment.

The difference between multimodal and intermodal transportation lies in the bill of lading and transport carrier responsibility of the shipment.

Intermodal containers

How do intermodal containers work?

An intermodal or ISO container is a container that is up to par with ISO standards. It can be used for storing and transporting materials and equipment within a global containerised intermodal freight transport system.

What do intermodal containers carry?

The most common items transported by intermodal containers are:

  • non-perishable cargo such as manufactured goods

  • temperature-sensitive perishable, chilled and frozen cargo such as seafood, meat, agricultural products, and medicines

  • non-perishable cargo that could be damaged in transport by condensation, like coffee and cocoa

  • oversized cargo like construction materials, heavy machinery and lumber

  • bulk hazardous or non-hazardous chemicals, oils, liquids, and food goods, shipped in tank containers

TEU - Twenty-foot- Equivalent Unit

A twenty-foot equivalent unit (TEU) is an intermodal container that measures 20 feet long, 8 feet wide, and 8 feet tall. A TEU can hold between 9 and 11 pallets, depending on whether they are standard pallets or EUR-pallets.

A forty-foot equivalent unit (FEU) is an intermodal container that measures about 40 feet long, 8 feet wide, and 8 feet tall. An FEU can hold between 20 and 24 pallets, depending on whether they are standard pallets or EUR-pallets.

Container payload

The payload is the weight of the cargo that a container can hold. This information can usually be found on the container door. The load weight must not exceed this value. However, the maximum load weight can differ per country, which means that sometimes the maximum load weight allowed is less than the number stated on the door.

Container tare weight

The tare weight is the total weight of the empty container. This must be taken into account when calculating the maximum authorised load weight of the container, due to country-specific weights per unit.

Containers types and sizes

Here is our curated list of the 8 most common types of shipping containers.

1. Dry storage containers

A dry storage container is the most commonly used intermodal container. It is mainly used for storing and transporting dry materials such as wooden or cardboard crates, pallets, barrels or drums.

This type of container is completely airtight and is not equipped with cooling nor ventilation systems like refrigerated and ventilated containers.

Dry storage containers are available in 20ft, 40 ft, and 10 ft. And, they are also available in High Cube ( Approximately 1 ft extra height compared to basic models).

2. Open top containers

An open top container falls within the category of dry storage containers. However, unlike a dry storage container, it does not have a roof.

This type of container is used to transport large items that are too heavy for manual handling or cannot fit into a standard dry storage container.

The opening of an open top container through smaller than the container’s interior. This means that there is less room for manoeuvring when loading your cargo through the top of an open top shipping container.

A 20 ft open top container has a maximum load of approximately 28 metric tons, while the 40 ft open top container can hold up to 30 metric tons.

© Transportplanning

3. Refrigerated shipping containers

Refrigerated shipping containers, also known as reefer containers, are equipped with a system that maintains an internal temperature of between -35ºC and + 15ºC.

These containers must always be connected to an external power source. And, they are mainly used for the shipment of temperature-sensitive, perishable cargo such as fish, meat, medicines and pharmaceutical products.

Reefer containers generally come in 20 ft and 40 ft, and they are commonly made from a weathering steel known as COR-TEN steel. And, they are also available in High Cube ( Approx. 1 ft extra height compared to basic models).


© MTcontainer

4. Open side containers

An open side container has the same features as a dry storage container. The main difference is the two additional bi-fold doors on one of the side walls. These bi-fold doors let you access one side of the container.

This type of container is useful when it comes to loading and unloading oversized materials. However, it is only available in a new or “one-trip” condition. A “one-trip” container is only shipped once (from the factory to the USA).

Open side containers are available in 20ft and 40ft. And, they are also available in High Cube ( Approx. 1 ft extra height compared to basic models).

© Containertech

5. Flat rack containers

Flat rack containers have collapsible sides that can be folded to make a flat rack. And, the end walls are stable enough to allow stacking several flat rack containers on top of one another.

These containers are especially suitable for heavy loads and cargo that need to be loaded from the top or sides, such as heavy machinery, pipes and construction materials.

Flat rack containers are manufactured from steel and come in 20 ft and 40 ft.

© Bison

6. Double door containers

Double door containers are standard intermodal containers. However, they have double doors on both ends. These containers are very durable and are helpful for quickly loading and unloading construction material such as steel and iron. Both sets of doors have the same locking assembling and weather-tight seals to protect cargo.

Double door containers are available in 20ft and 40ft. And, they are also available in High Cube ( Approx. 1 ft extra height compared to basic models).

© Mccontainers

7. Insulated containers

Similar to a refrigerated shipping container, an insulated container has a regulated temperature control that it uses to withstand a higher temperature.

Insulated containers are built for all year round use. They provide warm and dry storage space and basic models include pair doors and ventilation.

© Domertrade

Insulated containers are available in 20ft and 40ft.

8. Tank containers

Tank containers or tankers are intermodal containers used for transporting liquids, gasses and powders as bulk cargo.

They are made of steel or other anti-corrosive materials for the transportation and long-life protection of liquid materials.

A tank container must be at least 80% full to prevent dangerous surging of liquids in transit, but it must also not be over 95% full or there would not be sufficient room for thermal expansion.



Tank containers are only available in 20ft.

Table of standard container dimensions

The following table gives you the dimensions of 20-foot and 40-foot dry storage and reefer containers.

  Exterior Interior Door opening
  Length Width Height Length Width Height Width Height
20' Standard Dry Storage Container 20' 8' 8'6" 19'3" 7'8" 7' 9 7/8" 7'8" 7'5"
40' Standard Dry Storage Container 40' 8' 8'6" 39' 5" 7'8" 7' 9 7/8" 7'8" 7'5"
40' High Cube Dry Container 40' 8' 9'6" 39' 5" 7'8" 8' 10" 7'8" 8' 5 1/2"
20' Reefer Container 19' 10.5" 8' 8'6" 17' 11" 7'6" 7'6"* 7''5" 7'3"
40' Reefer Container 40' 8' 8'6" 37' 11" 7'6" 7'6"* 7''6" 7'6"
40' High Cube Reefer Container 40' 8' 9'6" 37' 11" 7'6" 8'4"* 7''6" 8'4"

ISO containers are used to transport a wide range of goods and manufactured products. And, it is essential to use tracking software to pinpoint the exact location of these shipments at all times to meet important deadlines. Here is a list of the best software appvizer recommends for tracking intermodal shipments:

Best tools to track intermodal shipments

Freight forwarders and import-export companies need tools to manage their import-export business efficiently and offer the best service to each customer.

These tools are indeed essential to them: they facilitate the management and editing of mandatory documents, but also enable them to trace the goods, i.e. the containers.

MercuryGate TMS: An all-in-one system for intermodal transportation

MercuryGate is a transport management system that can be used for all types of shipments including road, rail, sea, or air freight.

MercuryGate TMS is easy to integrate with external software such as ERP systems and WMS systems. And, its platform lets shippers, third-party logistics providers, freight brokers, freight forwarders and carriers work together in a synchronized environment to plan and optimize shipments.

SAP Transportation Management: Transportation and Logistics Management Software

SAP Transport Management is a transportation management system that lets shippers, logistics service providers and carriers manage their transportation processes within a single platform.


    © SAP

    Its list of features include:

    • freight management
    • order management
    • analytics
    • transportation and demand planning
    • a collaboration portal
    • interactive freight tendering

    Preparing for the future of intermodal transportation

    Intermodal transportation has been growing rapidly for many years. And, as the UK's economy and population keeps growing, the demand for intermodal shipments will grow, too.

    In consequence, intermodal networks are preparing for this by setting up new terminals, increasing tunnel heights, enhancing service reliability and more.

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