Freight Basics
Understanding Container Shipping: Types, Sizes and Key Terms
Standard, high-cube, reefer, open-top and flat-rack containers explained — plus the terms you will see on every booking.
YMS Global Freight · · 6 min read
Standardised ISO shipping containers made global trade efficient: the same box moves by ship, rail and truck without the cargo being handled. Choosing the right container is the first step in planning an ocean shipment.
Common container types
| Type | Typical use | Approx. internal capacity* |
|---|---|---|
| 20′ standard (dry) | Heavy, dense cargo | ≈ 33 CBM |
| 40′ standard (dry) | General cargo | ≈ 67 CBM |
| 40′ high-cube | Light, voluminous cargo — about 30 cm taller | ≈ 76 CBM |
| Reefer (20′/40′) | Temperature-controlled goods | Slightly less than dry equivalent |
| Open-top | Tall cargo loaded by crane from above | Similar to dry equivalent |
| Flat-rack | Oversized and heavy machinery | Determined by cargo dimensions |
*Capacities vary by manufacturer and carrier. Usable volume is usually lower once packaging and load planning are considered, and maximum payload is set by the container and by road-weight rules.
Reading a container number
Every container carries a unique ISO 6346 code: a three-letter owner code, an equipment category letter (U for freight containers), a six-digit serial number and a check digit — for example ABCU 123456 0. This is the number used for tracking on carrier websites.
Key terms on a booking
- TEU / FEU — twenty-foot and forty-foot equivalent units, used to measure container capacity.
- POL / POD — port of loading and port of discharge.
- Cut-off — the deadline for cargo and documents before a sailing.
- VGM — verified gross mass: the declared weight of a packed container, required before loading.
- Free time — days allowed before demurrage or detention charges apply.
- Transshipment — transfer of a container between vessels at an intermediate port.
Choosing the right container
Dense cargo usually reaches its weight limit before the container is full, so a 20′ is often the better choice. Light, bulky cargo fills space before weight, so a 40′ high-cube offers the lowest cost per cubic metre. Cargo that is too tall or wide for a standard box needs open-top or flat-rack equipment and additional planning.
