Logistics guides · Freight
Shipping Container Types and Dimensions: How to Choose the Right Box
Compare the dimensions, capacity and payload of dry, reefer, open top, flat rack and ISO tank containers, and learn how VGM and road weight limits apply.
Choosing the wrong container is one of the most common reasons freight budgets overrun: cargo that does not fit through the door, a box that is legal at sea but overweight on the road, or a second container booked for the sake of a few cubic metres. This guide covers the ISO container types that carriers operate in and out of Vietnam, their typical specifications, how to match a container to your cargo, the SOLAS Verified Gross Mass (VGM) requirement and the road weight limits that often decide how much you can actually load.
ISO containers and how to read the codes
Most ocean containers are built to ISO 668 (external dimensions) and ISO 1496 (technical requirements). External width is almost always 8 feet (2.438 m); the differences are length (20, 40 or 45 feet) and height (8 ft 6 in for standard boxes, 9 ft 6 in for high cubes). Each container carries an ISO 6346 identification number (four letters, six serial digits and a check digit) and a size-type code such as 22G1 for a 20-foot dry box or 45G1 for a 40-foot high cube.
In quotations and bookings you will see short forms: GP or DC (general purpose or dry container), HC or HQ (high cube), RF or RH (reefer, reefer high cube), OT (open top), FR (flat rack) and TK (tank). Capacity is measured in TEU, the twenty-foot equivalent unit: a 20-foot box is 1 TEU and a 40-foot box is 2 TEU.
Typical specifications at a glance
The figures below are typical values. Tare weight, internal dimensions and maximum payload vary by manufacturer, build year and carrier, so always check the data plate on the container door or confirm with the carrier before loading heavy cargo.
| Type | Internal L × W × H (m) | Capacity (m³) | Tare (kg) | Max payload (kg) |
|---|---|---|---|---|
| 20GP | 5.90 × 2.35 × 2.39 | ~33 | ~2,200–2,300 | ~28,000 |
| 40GP | 12.03 × 2.35 × 2.39 | ~67 | ~3,700–3,800 | ~26,500–26,700 |
| 40HC | 12.03 × 2.35 × 2.69 | ~76 | ~3,900–4,000 | ~26,500 |
| 45HC | 13.55 × 2.35 × 2.69 | ~86 | ~4,800 | ~27,500–28,000 |
| 20RF | 5.44 × 2.29 × 2.27 | ~28 | ~3,000 | ~27,000 |
| 40RH (reefer high cube) | 11.58 × 2.29 × 2.55 | ~67 | ~4,500–4,800 | ~29,000 |
| 20OT / 40OT | Close to the equivalent GP, removable tarpaulin roof | ~32 / ~65 | ~2,300 / ~3,900 | ~28,000 / ~26,500 |
| 20FR / 40FR | Floor ~5.6 / ~12.0 m, no side walls or roof | — | ~2,700 / ~5,000 | ~31,000 / ~40,000 |
| 20ft ISO tank | 14,000–26,000 litre tank in a 20ft frame | 14–26 (thousand litres) | ~3,500–4,200 | Depends on liquid density |
Most 20ft and 40ft containers have a maximum gross mass of 30,480 kg, and newer units are often rated at 32,500 kg or more. In practice, the binding limit is usually road legislation or carrier policy rather than the box itself.
What each type is used for
Dry containers: 20GP, 40GP, 40HC and 45HC
The 20GP suits heavy, dense cargo such as ceramic tiles, stone, small steel coils, bagged chemicals and rice. It offers only about 33 m³ but accepts close to 28 tonnes, so it is the natural choice when cargo weighs out before it cubes out. The 40GP and 40HC are for light, bulky goods such as furniture, garments, footwear and household electronics. A 40HC is about 30 cm taller than a 40GP, adding almost 9 m³, and on many trade lanes it costs the same or only marginally more, which is why it has become the default box for consumer exports. The 45HC adds roughly 1.5 m of length, but not every terminal, depot or road network accepts it, so check before you book.
Reefer containers
Reefers have an integral refrigeration unit that holds a set temperature, typically somewhere between about minus 30 °C and plus 30 °C depending on the model. They carry frozen seafood, meat, fresh fruit, pharmaceuticals and temperature-sensitive chemicals. Thick insulated walls mean a smaller interior than a dry box. When booking, provide the set point, ventilation setting and any humidity requirement, and ask for a pre-trip inspection (PTI). Cargo must be pre-cooled to carrying temperature: a reefer is designed to maintain temperature, not to pull down warm cargo.
Open top containers
Open tops have a removable tarpaulin roof and roof bows, so cargo can be crane-loaded from above. They are used for tall machinery, sheet glass, stone blocks, logs and anything that cannot go through the doors on a forklift. If cargo protrudes above the walls it becomes out of gauge (OOG), which attracts surcharges and restricts stowage positions on board.
Flat racks
Flat racks have a floor and two end walls, fixed or collapsible, with no sides or roof. They handle heavy-lift and oversized cargo such as transformers, special vehicles, steel structures and boilers. Because cargo is usually over-width or over-height, carriers require drawings, lifting points, a lashing plan and specific approval. Very large pieces can be loaded across several flat racks or moved as break bulk.
ISO tanks
An ISO tank is a stainless steel vessel inside a 20-foot frame for liquids such as chemicals, vegetable oils, food additives and spirits. Tanks must be filled within the safe range set by the manufacturer and dangerous goods rules, commonly around 80 to 95 percent of capacity, to avoid surge when too empty or lack of expansion space when too full. Dangerous goods must be declared under the IMDG Code with a safety data sheet and a tank cleaning certificate. For non-hazardous liquids, a flexitank inside a 20GP is a common alternative.
How to choose the right container
- Define the cargo: dry or temperature-controlled, liquid or solid, dangerous or not, in gauge or oversized.
- Calculate volume and weight from a detailed packing list with the dimensions and weight of every package. Real loadable volume is usually 85 to 90 percent of the theoretical figure because of gaps, pallets and stacking limits.
- Compare density: heavy, dense cargo usually fits best in a 20GP, while light and bulky cargo belongs in a 40HC.
- Check door openings: a dry container door is about 2.34 m wide and 2.28 m high (about 2.58 m on a 40HC). Anything larger needs an open top or a flat rack.
- Check road weight limits at both ends of the journey, in Vietnam and in the destination country.
- Book reefers, open tops, flat racks and 45HCs early, as equipment is limited, especially in peak season.
VGM: the SOLAS Verified Gross Mass requirement
Since 1 July 2016, amendments to SOLAS Chapter VI, Regulation 2 require every packed container to have a Verified Gross Mass before it is loaded on a ship. The shipper named on the carrier’s bill of lading is responsible for submitting the VGM to the carrier and terminal before the VGM cut-off. A container without a VGM will not be loaded.
SOLAS allows two methods. Method 1 is weighing the packed and sealed container on calibrated equipment. Method 2 is weighing all cargo, packaging, pallets and dunnage and adding the tare weight shown on the container door; it must follow a procedure accepted by the competent authority. Tolerances are not set by SOLAS but by each country or terminal, so declare a measured figure rather than an estimate.
VGM is not the cargo gross weight on the bill of lading. VGM = cargo + packaging + dunnage + container tare. An incorrect VGM can lead to a container being refused for loading, with storage and rollover costs.
Road weight limits in Vietnam
A 20-foot container may be rated for almost 28 tonnes of cargo, but that does not mean a truck may legally carry that weight on public roads. Vietnamese rules limit the gross weight of the whole combination (tractor, trailer, container and cargo) and the load on each axle, depending on the number and spacing of axles, and individual bridges and roads also have posted limits.
In practice, a common tractor and semi-trailer combination has a permitted gross weight of around 40 tonnes, depending on axle configuration. Once the tractor, chassis and container tare are deducted, the cargo you can legally carry is often well below the payload printed on the box. Overloading risks fines, forced offloading and safety incidents. For steel, tiles, stone and minerals, plan the tonnage per container in advance, or use barge or rail for the inland leg.
- Ask your trucking provider for the tractor and trailer configuration and unladen weights to calculate the maximum cargo per box.
- Check road limits in the destination country too; many markets are stricter than Vietnam.
- Distribute weight evenly across the floor; cargo concentrated at one end can overload an axle even when total weight is legal.
- Oversized and heavy-lift cargo needs a special road permit and may require a route survey.
Inspect the container before stuffing
Before loading, inspect the empty container: no holes or light leaks with the doors closed, a dry floor free of nails, no odour, intact door seals and a valid CSC plate. Food and agricultural cargo needs a clean, food-grade box. Photograph the container before, during and after loading and record the container and seal numbers; this evidence is essential if a damage, moisture or shortage claim arises later. GLG can combine equipment inspection, dunnage advice and loading supervision for high-value or sensitive shipments.
Frequently asked questions
How many cubic metres fit in a 40HC?
The theoretical capacity is about 76 m³, but realistic loadable volume is usually around 65 to 68 m³ depending on package sizes, pallets and stowage.
Should heavy cargo go in a 20GP or a 40GP?
Dense cargo is usually cheaper in a 20GP, which carries a similar weight to a 40GP at a lower rate. The real limit is normally road weight, not volume.
Who is responsible for the VGM?
The shipper named on the carrier’s bill of lading must submit the VGM before the cut-off, although a forwarder can do it on the shipper’s behalf.
Can a reefer cool down warm cargo?
It should not be used that way. Reefers maintain temperature, so cargo must be pre-cooled to carrying temperature before loading.
This content is for general guidance and does not replace legal or banking advice for a specific transaction.