Container glossary
What do “a twenty” and “a forty” mean in shipping?
“A twenty” is a 20 ft container and “a forty” is a 40 ft container — the everyday names used by port workers, truckers and freight forwarders, with “a forty-five” for the 45 ft. The words give the length only; height and type have to be said separately.
A twenty and a forty, measured
| Container | External L × W × H | Volume | TEU |
|---|---|---|---|
| 20 ft container | 6.06 × 2.44 × 2.59 m | 33.2 m³ | 1 |
| 40 ft container | 12.19 × 2.44 × 2.59 m | 67.7 m³ | 2 |
Data: ISO 668:2020
How the trade shortens a container to one word
Container lengths are few, so the length alone identifies the box in conversation: “two twenties and a forty on the next vessel”. Type is added when it matters — “high cube forty”, “reefer twenty”, “forty open top” — and on paper the same thing is written 20 GP, 40 HC or 40 RF, or as the ISO size and type code painted on the box, such as 22G1 or 45G1.
The slang maps onto the unit the industry counts in. A twenty is one TEU and a forty is two, which is why a forty is also an FEU; the table above sets the two side by side. Neither is exactly its nominal length. A forty is 76 mm longer than two twenties, so that two twenties with a gap between them occupy the place of one forty on a ship.
Where you hear it, and what to write instead
You hear it on the phone with a forwarder, at a depot gate, from a haulier quoting a delivery, and in rate sheets headed 20′ and 40′. It is speech. In a booking, a purchase order or a request for a quote, write the full description — length, height and type — because the line assigns equipment from what is written. “40 HC” and “40 GP” are different boxes, and a depot asked for “a forty” will hand over whichever it has.
If you are still choosing between the two lengths, the decision is weight against volume and is worked through in 20 ft vs 40 ft. Every size and type is listed in the dimensions chart.
Assuming “a forty” settles the height
The mistake is to hear “forty” and plan for the wrong one. A standard forty is 2.591 m tall outside and a high cube forty 2.896 m; inside, that is 67.7 m³ against 76.4 m³. Cargo planned to the high cube’s height does not go into a standard box, and a high cube delivered where a standard one was expected may not pass under a canopy or a low bridge on the way. On deep-sea trades the high cube is the dominant forty, so the slang often means one box while the paperwork names the other.
A second trap is thinking a forty carries twice what a twenty does. It holds twice the volume but not twice the weight: the standard twenty and forty share one maximum gross rating, and the longer box spends more of it on its own steel.
Frequently asked questions
Is “a forty” a standard or a high cube container?
It can be either — the word gives only the 40 ft length. Say “forty standard” (40 GP) or “high cube forty” (40 HC): the high cube is 2.896 m (9′6″) tall outside, the standard 2.591 m (8′6″).
How many TEU is a forty?
A forty is 2 TEU, which is the same as 1 FEU. A twenty is 1 TEU, and a forty-five counts as 2.25 TEU.
Is a twenty exactly 20 feet long?
No — a twenty is 6.058 m (19′11″) long, slightly under its nominal 20 ft. The shortfall leaves room for a gap when two twenties stand in the space of one forty.