What is a shipping container?
A shipping container is a standardised steel box built to carry goods by sea, rail, or road. Containers are designed to stack on ships, transfer between transport modes without unloading, and lock into position on trucks or trains. Most containers follow ISO standards so they can move between carriers and terminals worldwide without any modification.
If you have ever seen a quote from a freight forwarder offering a “20ft dry” or a “40ft HC reefer” and wondered what that actually means in practice, this article is for you.
Choosing the wrong container type is one of the most common and costly mistakes in shipping. It can delay your goods, damage your cargo, or leave you paying for space you cannot use. This article walks through every main container type, what each one is designed for, and how to match your cargo to the right box.
A shipping container is a reusable steel unit built for intermodal transport. That means it can move by sea, rail, and road without the cargo inside being touched between each leg. This is what makes global supply chains fast and cost-effective.
The concept was standardised in the 1950s and 1960s following the work of American entrepreneur Malcolm McLean. He recognised that the cost of loading and unloading cargo was the biggest expense in shipping, not the ocean crossing itself. By putting cargo in a sealed box that could be lifted between a ship, a truck, and a train, he cut port handling costs dramatically.
Today, around 800 million container movements take place every year across the world’s shipping lanes. The UK is one of the world’s busiest trading nations. The vast majority of goods imported from Asia, the Americas, and the Middle East arrive in a standard shipping container.
Containers are defined by their external dimensions and their purpose. Most follow ISO 6346, the international standard that governs container identification, coding, and marking. Understanding these dimensions and codes helps you communicate clearly with freight forwarders, shipping lines, and customs agents.
The standard dry container is the workhorse of global shipping. It is a sealed steel box with solid walls, a solid roof, and two doors at one end. It carries general cargo: anything that does not need refrigeration or special handling. Furniture, electronics, clothing, machinery parts, and consumer goods all move in standard dry containers every day.
There are two standard sizes: the 20-foot container (known as a TEU, Twenty-foot Equivalent Unit) and the 40-foot container. The TEU is the unit of measurement the entire shipping industry uses to count container volumes. When you see news about port congestion measured in “TEUs processed per day,” that is the 20ft container used as the baseline.
| Specification | 20ft Container | 40ft Container |
|---|---|---|
| External length | 6.06 m | 12.19 m |
| External width | 2.44 m | 2.44 m |
| External height | 2.59 m | 2.59 m |
| Internal length | 5.90 m | 12.03 m |
| Internal width | 2.35 m | 2.35 m |
| Internal height | 2.39 m | 2.39 m |
| Capacity (CBM) | Approx. 28 m³ | Approx. 57 m³ |
| Max payload | Approx. 21,600 kg | Approx. 26,500 kg |
| Tare weight | Approx. 2,200 kg | Approx. 3,800 kg |
| Door opening width | 2.34 m | 2.34 m |
| Door opening height | 2.28 m | 2.28 m |
The 20ft container works well for dense, heavy cargo. It reaches its weight limit before it fills its volume. The 40ft container works better for lighter, bulky goods. It gives you twice the volume for a relatively small increase in freight cost.
In practice, a 40ft container costs roughly 40–60% more than a 20ft on most routes, not double. If your cargo is light, a 40ft often gives better value per cubic metre.
High cube containers have the same footprint as a standard 40ft container but are 30 cm taller. The external height is 2.90 m instead of 2.59 m. The internal height increases from 2.39 m to 2.70 m, and the total usable volume rises from around 57 m³ to around 67 m³.
That extra 10 m³ matters more than it sounds. For cargo stacked on pallets, the added height can mean fitting one more layer. For lightweight goods such as mattresses, flat-pack furniture, or large machinery with a tall profile, the high cube is often the only option that works.
High cube containers are increasingly common on deep-sea routes. Many shipping lines now treat the 40ft high cube as their standard box rather than a specialist option. Check with your freight forwarder which container type is the default on your route, as this affects pricing.
| Specification | 40ft High Cube |
|---|---|
| External height | 2.90 m |
| Internal height | 2.70 m |
| Capacity (CBM) | Approx. 67 m³ |
| Max payload | Approx. 26,500 kg |
A 20ft high cube exists but is rare. Most carriers do not stock 20ft high cubes as standard equipment. If you need extra height in a 20ft footprint, check availability before booking. You may need to source a specialist operator.
A refrigerated container, or reefer, is a temperature-controlled unit fitted with its own mechanical refrigeration system. It can maintain internal temperatures from -30°C to +30°C, covering everything from deep-frozen fish to fresh flowers to pharmaceuticals.
Reefer containers have the same external dimensions as standard dry containers, either 20ft or 40ft, but the internal volume is smaller. The refrigeration unit takes up space at one end. A 40ft reefer typically has around 60 m³ of usable internal space compared to 67 m³ in a 40ft high cube dry box.
The refrigeration unit runs on electrical power supplied by the ship during the ocean leg. At ports and in depots, the container plugs into shore power. When moving by truck, a genset (generator set) can be attached to keep the temperature constant. You must confirm with your freight forwarder that each handling point on the route has reefer plug-in facilities. Gaps in the cold chain are a serious risk.
Reefers are used for:
Reefer freight costs considerably more than standard dry freight. On a UK import from Asia, a 40ft reefer typically costs £3,000–£6,000 more than a comparable dry container on the same route, depending on the carrier and season. Budget accordingly when quoting landed costs to your customer.
An open top container is a standard dry container with the roof removed and replaced by a removable tarpaulin cover. The end doors remain in place. The open roof allows cargo to be loaded from above by crane or forklift. This is useful when the cargo is too tall to fit through the doors.
Open top containers come in 20ft and 40ft sizes. Internal dimensions are the same as standard dry containers, aside from the open roof. The tarpaulin is secured over the top and bowed out over the cargo if needed. The cargo must not protrude more than a set limit above the container walls, typically around 30 cm for a “half-height over-height” load.
If your cargo exceeds the top of the container, this is called out-of-gauge (OOG) cargo. You need approval from the shipping line before booking. OOG cargo attracts additional charges and requires specialist stowage on the vessel. Your freight forwarder will need your cargo’s exact dimensions before booking.
Open top containers are commonly used for:
Loading an open top container usually requires a crane or overhead hoist at the origin warehouse. Confirm that your supplier has the right equipment before you agree on this container type.
A flat rack container is a steel platform with end walls but no side walls and no roof. It is designed for cargo that is too wide, too tall, or too heavy to fit inside a standard box. The cargo sits on the flat steel platform and is secured with lashing rings built into the structure.
Flat racks come in two versions. A collapsible flat rack has end walls that fold down flat, making empty flat racks easier to stack and store. A fixed flat rack has permanent end walls. Both are available in 20ft and 40ft lengths.
Flat rack cargo is exposed on the sides and top, so all goods must be properly protected against weather and seawater spray. Your freight forwarder will advise on tarpaulin wrapping, crating, or other weatherproofing measures. In some cases, specialist lashing companies are needed to secure the cargo safely.
Flat racks are used for:
Flat rack freight is priced differently from standard dry cargo. Shipping lines charge based on the footprint of the cargo, any overhang beyond the container frame, and the weight. Get a precise cargo measurement, including height, width, and length, before asking for a flat rack quote.
A tank container is a cylindrical tank mounted inside a standard ISO container frame. The frame is 20ft long, so it fits on the same ships, trucks, and trains as a standard 20ft container. The tank itself holds between 17,000 and 26,000 litres depending on the specification.
Tank containers carry liquids and gases that cannot be loaded into a standard dry box. They are built to carry three main categories of product:
Tank containers are usually owned or leased by specialist operators rather than bought by shippers. If you are moving bulk liquids, your freight forwarder will source the right tank type and specification for your product. You will need to provide a full product data sheet, including its UN number if it is a hazardous material.
Cleaning between cargoes is a regulated process. Many tank operators maintain detailed cleaning records for each tank. Buyers of food-grade products often require proof of the previous cargo before accepting a tank.
A ventilated container looks like a standard dry container from the outside but has small ventilation openings, typically slotted vents, built into the upper and lower side walls. Air moves through the container passively as the ship travels. This prevents the build-up of moisture, heat, and gases from cargo that breathes.
Ventilated containers are used for natural agricultural products that produce carbon dioxide or ethylene as they age. Without ventilation, these gases build up, causing spoilage, mould, and condensation damage. The most common cargoes include:
Do not confuse a ventilated container with a reefer. A ventilated container does not control temperature. It simply allows air exchange. If your cargo also needs to stay within a specific temperature range, you need a reefer with controlled atmosphere capability, not a ventilated box.
Ventilated containers are less common than standard dry boxes and are not stocked at every depot. Check availability on your specific route well in advance of booking.
Beyond the main types above, several specialist containers exist for specific cargo categories.
Bulk containers have a solid floor, solid walls, and hatches in the roof for top-loading dry bulk cargo: grain, sand, minerals, and similar materials. They are available in 20ft sizes and are used when the shipper wants containerised transport for cargo that would otherwise travel in bulk vessels or road tankers.
Car carrier containers are specialist open-frame containers designed to carry vehicles. Two or three cars can be loaded on adjustable ramps inside the frame. These are used for smaller vehicle volumes where a full RORO (Roll-on Roll-off) vessel shipment is not economical.
Half-height containers are standard dry containers built to half the normal external height, around 1.30 m. They are used for very dense, heavy cargo such as stone, scrap metal, and aggregates. A full-height container would be overloaded at the base before being full.
Insulated containers have insulated panels in the walls and roof but no active refrigeration unit. They slow the rate of temperature change but cannot maintain a set temperature. They are used for cargo that needs protection from extreme ambient temperatures rather than precise temperature control.
Understanding container types also means understanding how containers are booked.
FCL, Full Container Load means you book the entire container for your cargo. You fill it (or partly fill it) and it travels as a single unit. FCL is faster, more secure, and gives you direct control over the container’s contents. It is the right choice when your cargo fills 70–80% or more of a container, or when you have specific requirements around hygiene, security, or container type.
LCL, Less than Container Load means your cargo shares a container with other shippers’ goods. A consolidation agent or NVOCC (Non-Vessel Operating Common Carrier) groups multiple smaller shipments together, loads them into one container, and splits them again at the destination port. LCL typically costs around £50–£120 per cubic metre on common UK import routes from Asia, compared to a flat rate for an FCL that may start at £1,200–£2,500 for a 20ft box on the same route.
The container type choice matters here. LCL is only available for standard dry cargo in a standard dry container. If you need a reefer, an open top, a flat rack, or a tank, you are booking FCL. There is no LCL equivalent for specialist container types.
Use this table to match your cargo type to the right container.
| Cargo Type | Recommended Container | Key Consideration |
|---|---|---|
| General dry goods — furniture, clothing, electronics | 20ft or 40ft standard dry | Match size to cargo volume and weight |
| Bulky, lightweight goods — mattresses, flat-pack | 40ft high cube | Check forwarder’s standard box on your route |
| Fresh or frozen food | 40ft reefer | Confirm cold chain continuity at every port |
| Pharmaceuticals with temperature limits | 40ft reefer | Check GDP (Good Distribution Practice) compliance |
| Tall machinery, crane-loaded cargo | Open top 20ft or 40ft | Confirm crane access at origin |
| Very wide or heavy machinery | Flat rack 20ft or 40ft | Provide exact cargo dimensions before booking |
| Industrial or food-grade liquids | 20ft tank container | Provide UN number and product data sheet |
| Dry bulk — grain, minerals | Bulk container | Check if bulk vessel is more cost-effective at volume |
| Green coffee or cocoa beans | Ventilated 20ft | Check depot availability on your route |
| Mixed small shipment under 10 CBM | LCL (standard dry) | Compare FCL cost if shipment exceeds 15 CBM |
If you are unsure, share your cargo dimensions, weight, and any special handling requirements with your freight forwarder. A good forwarder will advise on the right container type and flag any handling requirements before the booking is made.
If you are buying or renting a container, for storage, on-site use, or conversion, you will see condition grades. Understanding these prevents you from overpaying or accepting a container that is not fit for purpose.
New (or “one-trip”) containers are built in Asia, predominantly China, and used once to ship cargo to Europe or the US before being sold. They are structurally sound with no major wear and usually under 12 months old. One-trip containers cost more but are the right choice for food-grade storage, pharmaceutical use, or conversion projects. Typical UK prices range from £2,200 to £3,500 for a 20ft one-trip box (as of 2026, though prices fluctuate with supply and demand).
Grade A (Cargo-worthy) containers are used boxes that have passed a survey and are certified fit to carry cargo. They may have dents, rust spots, and repaired panels, but the structure is sound, the floor is intact, and the doors seal properly. These are the most common grade for active shipping use. Prices vary with age and availability.
Grade B (Wind and Watertight) containers are older boxes not rated for sea transport but suitable for on-site storage where structural perfection is not needed. They keep out wind and rain but may not be suitable for sensitive goods. These are the cheapest option for static storage use.
Ask any seller or rental company for a current container inspection report. For one-trip or cargo-worthy containers, this is standard practice.
Every shipping container carries an identification code governed by ISO 6346. This standard defines how containers are identified and how their details are encoded. Understanding it helps you read shipping documents and identify your container accurately.
A typical container number looks like this: MSCU 123456 7
This breaks down as follows:
Containers also carry a size and type code: a four-character code that appears on the container and in shipping documents. For example:
| Code | Meaning |
|---|---|
| 22G1 | 20ft standard dry, one pair of doors |
| 42G1 | 40ft standard dry |
| 45G1 | 40ft high cube dry |
| 22R1 | 20ft refrigerated |
| 42R1 | 40ft refrigerated |
| 22U1 | 20ft open top |
| 22P1 | 20ft flat rack |
The size and type code appears on your Bill of Lading, your arrival notice, and your customs declaration. Make sure the code on your shipping documents matches the container that was loaded at origin.
Since the UK left the EU’s customs union, every container arriving in the UK requires a full UK customs declaration, regardless of container type. This applies whether you are importing a 20ft standard dry box from China or a tank container of food-grade oil from the Netherlands.
The declaration is filed through the UK Customs Declaration Service (CDS), which replaced the old CHIEF system. You or your customs broker must have a UK EORI (Economic Operators Registration and Identification) number to do this. If you do not have one, apply through HMRC before your first shipment.
Container type affects your customs process in the following specific ways:
Reefer containers carrying food of animal origin (meat, fish, dairy) must enter the UK through a Border Control Post (BCP) with cold chain facilities. Not all UK ports have BCPs, and not all BCPs handle all commodity types. Check the DEFRA approved BCP list before booking your freight. Failing to route your reefer through an approved BCP will result in the goods being held or rejected at port.
Tank containers carrying chemicals must be declared with the correct UN number and commodity code. HMRC may require additional documentation including safety data sheets. Hazardous goods declarations must also comply with the UK’s implementation of the IMDG Code.
Open top and flat rack containers carrying out-of-gauge cargo may attract specific inspection procedures at ports. Ports must log and inspect unusual loads, and clearance can take longer than for standard dry containers. Build extra time into your schedule for OOG shipments.
UK import duty rates have not changed based solely on container type. The commodity code for your goods determines the tariff, and that applies regardless of how the goods arrive. Post-Brexit, goods arriving from the EU are no longer automatically exempt from import duty unless they qualify under the UK-EU Trade and Cooperation Agreement (TCA) and carry the correct proof of origin.
If you are importing goods from EU suppliers that previously moved duty-free under single market rules, check with your customs broker whether those goods now qualify under TCA preferential rates and what documentation your supplier must provide.
What is the most common type of shipping container?
The 40ft standard dry container is the most commonly used container in global shipping. It offers the best balance of volume, payload, and cost for general cargo. On many major routes from Asia to the UK, the 40ft is the default unit quoted by shipping lines.
What is the difference between a 20ft and 40ft container?
A 20ft container has around 28 m³ of internal space and can carry up to about 21,600 kg of cargo. A 40ft container has around 57 m³ and can carry up to about 26,500 kg. The 40ft gives you roughly double the volume for around 40–60% more freight cost on most routes. Choose the 20ft for dense, heavy cargo; choose the 40ft for lighter, bulky goods.
What is a high cube container?
A high cube (HC) container has the same length and width as a standard container but is 30 cm taller. A 40ft high cube has an internal height of 2.70 m compared to 2.39 m in a standard 40ft. The extra height gives around 67 m³ of internal volume, useful for tall or bulky goods.
Can I use a standard dry container for food?
Yes, for dry food products that do not require temperature control. Rice, pulses, tinned goods, and packaged dry products commonly travel in standard dry containers. If your food product is fresh, frozen, or requires a specific temperature range, you need a reefer.
What does FCL and LCL mean?
FCL means Full Container Load: you book the whole container. LCL means Less than Container Load: your cargo shares a container with other shippers’ goods. LCL is usually cheaper for small shipments but adds transit time because cargo must be consolidated at origin and deconsolidated at destination.
Do I need a different container for importing from the EU after Brexit?
No, the physical container type is determined by your cargo, not the trade route. But all containers arriving in the UK from the EU now require a UK customs declaration. Goods that previously crossed from EU countries without customs formalities now need a full import entry filed through the UK Customs Declaration Service (CDS).
How do I know if my cargo is out-of-gauge (OOG)?
Your cargo is OOG if it exceeds the internal dimensions of the container it is loaded into, or if it protrudes beyond the container frame when loaded on a flat rack. You must declare OOG cargo to the shipping line before booking. OOG shipments attract surcharges and require specialist stowage approval.
What is ISO 6346?
ISO 6346 is the international standard for container identification and coding. It defines the owner code, serial number, check digit, and size/type code that appear on every shipping container. These codes appear on your Bill of Lading and customs declarations. Understanding them helps you verify that your shipping documents match the physical container.
Word count: around 3,100 words
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