Container Types
Container types explained
A dry container — also called a GP (general purpose) container — is the standard enclosed steel box with no insulation or cooling, and it carries most of the world's containerised cargo. Where that does not fit, there are reefer, open top, flat rack and tank types. Here is what each one is built for, and how they differ in usable space.
Quick overview
Find the right type fast
| Type | Key feature | Main use |
|---|---|---|
| Dry | The standard enclosed box | Most general cargo |
| High Cube (HC) | ~30cm taller than dry | Bulky or tall cargo |
| Reefer | Built-in refrigeration unit | Produce, seafood, food, pharma |
| Open Top | Open roof, tarpaulin cover | Tall cargo, crane loading |
| Flat Rack | No sides or roof, floor only | Heavy equipment, timber, oversized cargo |
| Tank | Cylindrical tank in a frame | Chemicals, edible oil, spirits |
Detailed look
Dry Container (Dry / GP)
An enclosed steel box with no insulation or cooling, accounting for the vast majority of container traffic worldwide. Used broadly for general cargo that doesn't need temperature control.
Reefer Container
Fitted with insulation and a refrigeration/cooling unit to hold a set temperature. Because the cooling unit sits at the front, internal volume is smaller than a dry container of the same nominal size.
Open Top Container
Has an open roof so cargo taller than the container can be loaded from above by crane. The top is covered with a waterproof tarpaulin.
Flat Rack Container
No sides or roof — just a floor and two end walls — for oversized cargo like heavy equipment, machinery, and timber that exceed standard width or height.
Tank Container (ISO Tank)
A cylindrical tank mounted inside a frame, used to transport liquid or gas cargo such as chemicals, edible oils, and spirits.
Dry vs reefer — what actually differs
Both are enclosed steel boxes of the same nominal length, so on a booking they look interchangeable. They are not. A reefer gives up a significant share of its internal space to insulation and the cooling unit, and it costs more to run because it needs power the whole way.
| Dry (GP) | Reefer (RF) | |
|---|---|---|
| Temperature control | None | Set point held throughout |
| 20ft internal (approx.) | 589 × 235 × 239 cm | 545 × 229 × 225 cm |
| 40ft HC internal (approx.) | 1203 × 235 × 269 cm | 1157 × 229 × 250 cm |
| Space penalty | — | Roughly 10–12% less volume |
| Power | Not required | Required at origin, on board, at transhipment, at destination |
| Typical cargo | General cargo, machinery, packaged goods | Produce, seafood, dairy, pharmaceuticals |
| Availability | Widely available | Smaller fleet, book earlier |
The practical consequence is that you cannot reuse a dry container load plan for a reefer. A 40ft reefer is about 46cm shorter inside than a 40ft HC dry box, which is often a full row of cargo. If your quantity was calculated on dry dimensions and the booking switches to a reefer, the count has to be redone.
The other difference that catches people out is the floor. Reefers use a T-bar floor so cold air can circulate underneath, and blocking that airflow defeats the cooling. Cargo generally should not be stacked tight to the ceiling either — most reefers have a red load line marking the limit.
Before you commit to a special equipment box
Availability is not like dry. Dry containers sit in most ports in quantity. Open tops, flat racks and tanks exist in far smaller fleets, so on some trades and at some times of year you wait. If the sailing is fixed, confirm equipment availability before anything else.
Cargo that breaks the envelope is priced separately. Open tops and flat racks let cargo sit proud of the container, but out-of-gauge (OOG) cargo attracts surcharges based on how far it protrudes and in which direction, and may block adjacent slots. It is not a casual upgrade for cargo that is slightly too big.
Securing responsibility often sits with the shipper. A dry box contains the cargo on all sides. A flat rack gives you a deck and two end walls. If lashing fails, the damage is rarely limited to your own cargo, so establish who is responsible for securing and to what standard before booking.
A reefer is only as good as its power. Beyond the set point, confirm that power is maintained through transhipment and whether a temperature recorder travels with the unit.
Calculate dry / HC container loading now
Get a free piece count and layout drawing for the most common 20ft, 40ft and 40ft HC dry containers.
Open the Loading SimulatorFAQ
Common questions about container types
What's the most commonly used container?
The dry container (GP). Most general cargo that doesn't need temperature control ships in 20ft or 40ft dry containers.
Why does a reefer have less volume?
A front-mounted refrigeration unit and insulated walls reduce internal dimensions. Even at the same nominal 40ft length, it has roughly 10%+ less volume than a dry container.
What does "dry container" mean?
A dry container (also called GP, for general purpose) is a standard enclosed steel shipping container with no insulation, cooling or ventilation. It carries general cargo that does not need temperature control, and accounts for the large majority of container shipments worldwide.
What is the difference between a dry container and a reefer container?
A reefer has insulated walls and a built-in refrigeration unit that holds a set temperature; a dry container has neither. The trade-off is space and cost: a reefer loses roughly 10–12% of internal volume to insulation and machinery, and needs power at every stage of the journey. A 40ft reefer is about 46cm shorter inside than a 40ft HC dry container, which is often a full row of cargo.
What container should I use for tall cargo?
If you just need more height, use a 40ft High Cube. If cargo exceeds the container's height entirely, use an open top or flat rack.