If you've heard the term "conex box" and wondered whether it's different from a shipping container, the short answer is: they're the same thing. "Conex" is the older military and industrial name for what the commercial world calls a shipping container. Today the two terms are used interchangeably — though "conex" is still far more common in construction, military, and rural settings.
The quick answer: A conex box is a standardized steel storage container — typically 20ft or 40ft long — originally developed for US military logistics in the 1950s. They are structurally identical to the ISO shipping containers used in international trade and sold commercially today. The word "conex" is a shortening of "Container Express," the military's original designation for the program.
In this guide
History: where the name "conex" comes from
The conex box has its origins in US military logistics. In the early 1950s, during the Korean War, the US Army was struggling with cargo handling — supplies were packed in individual crates and bags that had to be manually loaded and unloaded at every transfer point. The system was slow, labor-intensive, and resulted in significant cargo loss.
In 1952, the Army Transportation Corps developed a standardized steel container they called the "Conex" — short for Container Express. The original Conex was a 6x6x8ft steel box specifically designed to move supplies from ships to depots to frontline units without being opened in transit. By the Vietnam War era, the Conex had evolved into the larger 8x8x20ft format that became the global ISO standard.
By the 1970s, the ISO shipping container standard had been adopted worldwide, and the term "shipping container" became dominant in commercial use. But the military, construction industry, and rural communities continued — and still continue — to call them conex boxes. The name stuck because an entire generation of veterans, engineers, and contractors grew up using it.
Conex vs shipping container: what's the difference?
Functionally and structurally, there is no difference between a conex box and a shipping container. They are the same product with two names. Both meet ISO standards, both use the same corner castings, both are made of Corten weather-resistant steel, and both are available in the same standard sizes.
Conex box
Military / industrial / rural terminology
Shipping container
Commercial / trade terminology
Search tip: use both terms when buying
When searching for suppliers, try both "conex box for sale" and "shipping container for sale" in your area. Some local suppliers use one term, some use the other. You'll reach different inventory by searching both.
Conex box sizes and dimensions
Conex boxes come in three standard sizes used in the US market. The 20ft is the most common for storage and transport. The 40ft standard and 40ft high cube are preferred for conversions where interior space matters.
20ft Conex
The original military standard
40ft Conex
Standard long-form unit
40ft High Cube
Extra foot of headroom
High cube conex boxes are the preferred choice for any conversion project — the extra foot of interior height makes a significant difference once you add a subfloor, ceiling panels, and HVAC equipment. For pure storage where headroom doesn't matter, a standard 20ft or 40ft is the better value. See the full container sizes guide for a complete breakdown including 10ft and 45ft units.
What are conex boxes used for?
The conex box's durability, security, and portability make it useful across a wide range of applications. Here are the most common uses.
On-site storage
The most common use — job sites, farms, ranches, and construction projects use conex boxes to store equipment, tools, and materials securely on location.
Best size: 20ft
Garage & workshop
A 20ft conex fits one car plus a workbench. A 40ft handles two vehicles, full tool storage, and workspace. Much cheaper than building a detached garage.
Best size: 40ft or 40ft HC
Container home
Conex boxes are used as the structural shell for permanent residences, ADUs, and vacation cabins. One 40ft high cube provides roughly 320 sq ft of living space.
Best size: 40ft high cube
Office & studio
Converted conex boxes make effective backyard offices, art studios, and meeting rooms. Add insulation, electrical, and HVAC for a professional working space.
Best size: 20ft HC or 40ft HC
Pool
Conex boxes are converted into above-ground or in-ground lap pools. A 20ft container makes a 20×8ft plunge pool. A 40ft container is a full lap pool.
Best size: 20ft or 40ft
Bunker & storm shelter
Buried conex boxes are used as storm shelters, bunkers, and emergency supply caches. The steel shell handles significant lateral soil pressure when properly reinforced.
Best size: 20ft
How much does a conex box cost?
Since conex boxes are physically identical to shipping containers, they carry the same price. The main variables are size, condition, and your distance from the nearest depot.
20ft conex box
$1,500–$5,500
- AS-IS (unknown condition) $1,000–$1,800
- WWT (wind & water tight) $1,500–$2,500
- CWO (cargo worthy) $2,000–$3,500
- One-trip (like new) $3,500–$5,500
- Delivery (50 mi) $300–$700
40ft conex box
$2,500–$9,000
- AS-IS (unknown condition) $1,500–$2,500
- WWT (wind & water tight) $2,000–$3,500
- CWO (cargo worthy) $2,800–$4,500
- One-trip (like new) $4,500–$7,500
- High cube add +$500–$1,500
Prices are before delivery and vary significantly by region. Port cities like Houston, LA, Savannah, and Seattle have the most inventory and lowest prices. Remote and landlocked areas pay 20–40% more for both the container and delivery. For a full breakdown including regional pricing, see our shipping container cost guide.
Budget for delivery separately
Always get a delivered-to-your-location price. A conex box quoted at $2,000 plus $900 delivery from a supplier 200 miles away may cost more than a $2,500 quote with $350 delivery from a local depot. Compare total delivered cost, not just the container price.
Renting a conex box
If you need a conex box for a construction project, event, or short-term storage, renting is often cheaper than buying. Monthly rental rates for a standard 20ft conex run $100–$200/month in most US markets, with 40ft units running $150–$300/month.
Most rental agreements include delivery and pickup. Minimum rental periods are typically 1–3 months. Month-to-month rentals after the minimum term are standard. Rent-to-own programs are also available — you pay monthly and a portion goes toward the purchase price, with the option to buy at the end of the term.
When renting a conex box, confirm:
- Whether delivery and pickup are included in the monthly rate or billed separately
- The minimum rental period and any early termination fees
- What condition the unit will arrive in (WWT is standard for rentals)
- Who is responsible for damage during the rental period
- Whether the unit can be modified during the rental (usually not)
See the full container rental guide and current rental prices by size and region for more detail.
Where to buy a conex box
Conex boxes are sold by container depots, leasing companies, and online marketplaces. The best prices are usually from regional depot suppliers who have inventory on hand rather than brokers who source from multiple locations.
When buying, confirm the exact condition grade — not just "used." Sellers sometimes describe heavily damaged containers as "used" without disclosing the condition grade. Ask specifically whether the unit is WWT, CWO, or AS-IS, and what that means for their company's grading criteria.
For conversions — especially homes and offices — one-trip containers are worth the premium. Used containers may have residue from prior cargo, floor damage, or rust that isn't visible in photos. Starting a livable conversion from a clean, structurally sound one-trip unit avoids expensive remediation down the line.
Compare conex box prices near you
Shipped.com carries 20ft and 40ft conex boxes across the US in multiple condition grades, with delivery estimates to your location.
See prices and availability →Frequently asked questions about conex boxes
What is a conex box?
A conex box is a standardized steel storage and transport container — typically 20ft or 40ft long — originally developed for US military logistics in the 1950s. The name is short for "Container Express," the Army's original designation for the program. Today, conex boxes and shipping containers are the same product with different names: "conex" is common in military, construction, and rural settings, while "shipping container" is the commercial term.
Is a conex box the same as a shipping container?
Yes. A conex box and a shipping container are structurally identical — same ISO dimensions, same Corten steel construction, same corner castings, same door configuration. The only difference is the name. "Conex" came from the US military in the 1950s; "shipping container" became the dominant commercial term by the 1970s. When you search for prices, search both terms — different suppliers use different names for the same product.
How much does a conex box cost?
A used 20ft conex box in cargo-worthy (CWO) condition costs $2,000–$3,500 before delivery in most US markets. New (one-trip) 20ft units run $3,500–$5,500. Used 40ft units cost $2,800–$4,500, and one-trip 40ft units are $4,500–$7,500. Delivery adds $300–$2,000 depending on your distance from the nearest depot. See the full price guide for regional breakdowns.
What are the dimensions of a conex box?
Standard conex box dimensions: a 20ft unit is 20ft long × 8ft wide × 8ft 6in tall externally, with an interior height of 7ft 10in and about 160 sq ft of floor space. A 40ft unit is 40ft long × 8ft wide × 8ft 6in tall externally, with about 320 sq ft of floor space. The 40ft high cube adds 1ft of height (9ft 6in external, 8ft 10in internal) — useful for any conversion project where headroom matters.
How much does it cost to rent a conex box?
Monthly rental rates for a 20ft conex box run $100–$200/month in most US markets. A 40ft unit rents for $150–$300/month. Most rental agreements have a 1–3 month minimum. Delivery and pickup are usually billed separately — add $300–$800 each way. Rent-to-own programs are also available, typically with a portion of monthly payments applying toward the purchase price.
Can you use a conex box as a garage?
Yes — a conex box garage is one of the most popular alternative garage solutions. A 20ft conex fits one car plus storage. A 40ft fits two cars in a front-to-back configuration or one car with a full workshop. The main trade-off is width: at 7ft 8in interior width, doors can only open partially inside the container. Adding a roll-up garage door to the end is a popular modification that solves the access problem. See our container garage guide for full details.
Can a conex box be buried underground?
A conex box can be partially or fully buried, but it requires specific structural modifications. Standard containers are designed to carry weight on their corner castings — not to resist lateral soil pressure across their walls. Burying a container without reinforcement can cause wall collapse under soil load. For an underground bunker or storm shelter, the side walls need steel reinforcement, typically I-beam ribs welded horizontally every 2–3 feet, before burial. Hire a structural engineer to design the reinforcement before excavating.
How long does a conex box last?
A well-maintained conex box lasts 25–30+ years. The Corten steel construction is specifically designed to resist corrosion — it develops a stable rust-colored patina that actually protects the metal underneath. The main longevity risks are: floor rot (check and seal the wooden floor boards), roof rust (inspect seams annually), and door seal deterioration. One-trip containers in good condition can last 40+ years with basic maintenance.
Where can I buy a conex box near me?
Conex boxes are sold by regional container depots, leasing company resellers, and online container marketplaces. Search for "shipping container for sale" or "conex box for sale" plus your city — both terms reach different suppliers. Port cities (Houston, LA, Savannah, Seattle, Baltimore) have the most competitive pricing. The further you are from a major port, the higher your delivery costs will be. Always get three quotes and compare the all-in delivered price, not just the container price.
What is the difference between a conex and a MILVAN?
A MILVAN is a specific military-spec version of the standard ISO container — the name stands for Military Van Container. MILVANs meet ISO standards plus additional military specifications for door locking, floor load rating, and stackability under military logistics conditions. For civilian purposes, the distinction doesn't matter — both MILVANs and conex boxes are the same dimensions and can be used interchangeably. You'll occasionally see surplus MILVANs sold at government auctions.