What Is a Conex Box?
Where the name comes from
In 1948 the US Army’s Transportation Corps built the Transporter, a corrugated steel box with double doors at one end that carried up to 9,000 lb of supplies, about 8′6″ long. After it proved itself in Korea, the Army turned it into the CONEX system in late 1952, adding a half-size unit and boxes that stacked three high. By 1965 the military had some 100,000 of them, and more than 100,000 more followed for Vietnam. The commercial shipping container that took over world trade is larger and built to ISO standards, but the Army kept calling it a CONEX, and the word passed into everyday American use for any steel shipping container.
Conex, shipping or storage container?
Conex box, shipping container, cargo container, sea container, intermodal container and ISO container all describe the same steel box: sellers use the names interchangeably, and so do we. “Intermodal” means it moves between ship, train and truck without being unpacked. In the container trade, “storage container” usually means the same thing, a shipping container sold for use on land, often a used one in the wind and watertight grade.
One name is different: portable storage. Search for portable storage containers and most results are moving-company units, rented, dropped off and picked up full, not steel conex boxes you buy and keep. If you want a container that stays, look for conex or shipping containers. All shipping containers.
Conex box sizes and prices
| Conex size | Outside (L × W × H) | Floor inside | Used | New |
|---|---|---|---|---|
| 10ft | about 10′ × 8′ × 8′6″ | 71 sq ft | — | $4,650 |
| 20ft | 19′10½″ × 8′ × 8′6″ | 150 sq ft | $1,400 | $2,750 |
| 40ft | 40′ × 8′ × 8′6″ | 305 sq ft | $1,900 | $5,350 |
| 40ft high cube | 40′ × 8′ × 9′6″ | 305 sq ft | $1,980 | $3,900 |
Longer boxes exist too: a 45ft high cube and a 53ft domestic container, both priced here used, with new ones quoted on request. Full measurements, inside and out: shipping container dimensions. High cubes add a foot of height: high cube vs standard.
New or used
A used conex box has crossed the ocean for years before it’s retired and sold, and comes graded: cargo worthy if it’s still fit for shipping, wind and watertight if it’s sold for storage. A new one, called one-trip, has made a single voyage, usually from Asia, and arrives with clean paint and an unworn floor, for $2,750 against $1,400 used for a 20ft this week. For storage, a used wind and watertight conex is all you need; for an office, a shop or a box in plain view, one-trip is worth the difference.
Renting instead? Conex boxes rent from $95 a month for a used 20ft on a 12-month term, before delivery and pickup: container rental.
What people use conex boxes for
Most end up as storage: on a farm, a job site, a business lot or behind a house. Others become site offices and workshops, and with insulation or a roll-up door they turn into climate-controlled or easy-access storage. Container offices · insulated containers · roll-up door containers.
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Frequently asked questions
Why is it called a conex box?
After the US Army’s CONEX, for “Container Express,” the steel shipping box its Transportation Corps developed in late 1952 from an earlier 1948 design called the Transporter. The US military kept the name for the larger standard containers that came after, and it stuck in American English.
Is it CONEX or connex?
CONEX, from CONtainer EXpress; “conex box” in everyday writing. “Connex” is a common misspelling of the same word, and sellers use both for the same steel container.
How much does a new conex box cost?
This week, a new one-trip conex starts at $2,750 for a 20ft, $3,900 for a 40ft high cube, $5,350 for a standard-height 40ft, before delivery and sales tax. The small 10ft starts at $4,650. New conex boxes.
What is a conex storage box?
A conex box bought or rented for storage on land rather than for shipping: usually a used container in the wind and watertight grade, set on a yard, a farm or a job site. Container grades.
Sources
History of the CONEX: the US Army Transportation Museum’s account, with the National Research Council and Marc Levinson’s The Box (2006), as gathered in Wikipedia’s “Conex box” article. Naming in today’s market: the guides and listings of US container sellers, and our own review of search results for “portable storage.” Sizes: ISO 668 and carrier and lessor spec sheets. Prices: our weekly record of starting prices, week of Oct 21, 2026.