A conex box is a shipping container. It's the same steel box, with the same 8 ft width, corner castings and cargo doors, and "conex" is an old military name that stuck to it. The word survives mostly among people who picked it up in the service or on a jobsite. If you came here worried you've been searching for the wrong thing, you haven't. Anything sold as a shipping container, sea can, storage container or ISO container is what you're after.
The rest of this page covers what most people want next: sizes, delivered prices and how to buy one.
Conex box, shipping container, sea can: same thing
The name changes with region and trade. "Conex" and "conex box" are common in the US, especially among people with a military or construction background. "Sea can" is the usual word in Canada. "ISO container" is the engineering term, since the boxes are built to ISO 668 dimensions. Retailers say "storage container" once the box stops traveling, and shipping lines say "intermodal container" because the same box moves by ship, rail and truck without being unpacked.
The word a seller uses doesn't change the box, but the grade and the dimensions do. The shipping containers for sale page lays out every size and grade we sell, and all of it applies to a conex box.
Where the word conex comes from
Conex is short for "container express." In 1948 the US Army developed a reusable steel box called the Transporter, about 8 ft 6 in long, 6 ft 3 in wide and 6 ft 10 in high, that could be lifted, stacked and moved by ship, rail and truck without being unpacked. After it proved itself in Korea, the Army built it into the CONEX system in late 1952. By 1965 the US military had about 100,000 CONEX boxes, more were bought for the Vietnam War, and the word stuck with everyone who handled them.
The box you buy today comes from a parallel line. In 1956 a trucking operator named Malcom McLean shipped 58 containers from Newark to Houston on a converted tanker, the Ideal X, and the ISO standards that fixed the 8 ft width and the 20 and 40 ft lengths followed from 1968. Modern containers are ISO boxes, not Army Transporters, but the nickname carried over.
Conex box sizes and dimensions
Four sizes cover almost every buyer. All are 8 ft wide outside and about 7 ft 8 in wide inside, so the choice comes down to length and height.
| Size | Outside (L x W x H) | Inside, about | Door opening, about | Floor, about | Empty weight, about |
|---|---|---|---|---|---|
| 10ft | 10' x 8' x 8'6" | 9'3" x 7'8" x 7'10" | 7'8" x 7'5" | 70 sq ft | 2,500 to 3,000 lb |
| 20ft standard | 20' x 8' x 8'6" | 19'4" x 7'8" x 7'10" | 7'8" x 7'5" | 150 sq ft | 4,800 to 5,100 lb |
| 40ft standard | 40' x 8' x 8'6" | 39'5" x 7'8" x 7'10" | 7'8" x 7'5" | 300 sq ft | 8,000 to 8,400 lb |
| 40ft high cube | 40' x 8' x 9'6" | 39'5" x 7'8" x 8'10" | 7'8" x 8'5" | 300 sq ft | 8,600 to 8,900 lb |
Standard ISO outside dimensions; individual units vary slightly by manufacturer and age. 10ft boxes are not a standard shipping size, so they vary more.
The 20ft is the one most people mean when they say conex box. It has about 150 sq ft of floor, holds roughly a one-car garage's worth of contents and is short enough for most driveways. 20ft containers are the most common size for homes, small farms and jobsites. A 40ft doubles the floor for well under double the price, and the high cube adds a foot of height for tall shelving and conversions. The full dimension chart has metric figures, cubic capacity and what fits through the door.
How much a conex box costs delivered
A conex box is priced by size and grade, plus delivery from the nearest yard. Enter your ZIP to see your delivered price.
A 10ft is priced on request because supply varies so much by area.
The price depends mostly on how far the box travels from the nearest container yard (delivery is usually the second-biggest line after the box), on grade and on local stock. Port cities and rail hubs tend to have more boxes and sharper prices than rural inland areas. The what drives the price guide takes a quote apart line by line.
Standard conex boxes with standard doors are also sold at one national price on our fixed-price containers pages. Delivery is a flat fee by size and method, the same anywhere in the contiguous US, and self pickup is free.
New vs used conex boxes
A new conex box is a "one-trip" container: built new, loaded once for the voyage over, then sold. It looks close to new and costs the most. A used conex box comes in two grades. Cargo-worthy means it was inspected and judged structurally sound to carry cargo, with a solid frame, floor and doors. Wind and watertight means it's retired from shipping and cosmetically rough, but it was sealed against wind and rain when inspected.
Used costs noticeably less than new on the same size. The rule we give people is to buy new if the box will be seen from the house or if you plan to insulate or cut into it, and to buy used if it goes out of sight and just has to stay dry. All three grades lock and keep the weather out. They differ in looks, structure and the years left in them.
There's one caveat with used boxes. Grades are judged at inspection, not by a government body, and some containers are sold by grade and picked at loading, so you won't always see the exact unit first. Ask for photos whenever they're available, and do the daylight test on delivery day: step inside, close the doors and look for light.
What people use them for
The box was built to keep cargo dry across an ocean, which is why it works for almost anything that needs to stay dry on land.
- Home and garage overflow during a move or renovation
- Farm and ranch supplies: feed, tack, tools and chemicals locked away from weather and animals
- Jobsite tools and materials, with a lock box on the doors
- Workshops, offices and studios, usually a new high cube with a personnel door, windows, insulation and power
- Seasonal inventory for small businesses, parked behind the shop
- Hunting camps and remote cabins, where a wooden shed would rot or be broken into
Compared with a stick-built shed, conex storage containers arrive finished and lockable the day the truck comes, and they can be picked up and moved again later.
How to buy a conex box
- Decide the job, then the size and grade. For storage out of sight, a used 20ft or 40ft. For anything visible or modified, new.
- Measure the spot and the route. A tilt-bed truck needs roughly 60 to 100 ft of straight approach for a 20ft and 100 to 150 ft for a 40ft, about 12 ft wide, with no low wires and firm ground.
- Check local rules and any HOA before you commit.
- Get a delivered price in writing that names the size, grade, doors, what's included and the delivery window. Compare delivered prices, never container-only prices.
- Inspect on delivery day while the driver is there.
The complete buying guide walks through each step with the questions to put to a seller. With us, step 4 is a single request: tell us your ZIP, size and grade, and a person on our team matches it to containers at the nearest yard and sends one delivered price, usually within 1 to 2 business hours. Nothing is ordered until you approve it.
Frequently asked questions
Is a conex box the same as a shipping container?
Yes. Conex is a nickname from the US Army's container express program, and the box itself is a standard ISO shipping container. Sizes, grades and prices are the same whichever word a seller uses.
How big is a standard conex box?
The two standard sizes are 20ft and 40ft, both 8 ft wide and 8 ft 6 in tall outside. A 40ft high cube is 9 ft 6 in tall. Inside, a 20ft is about 19 ft 4 in long, 7 ft 8 in wide and 7 ft 10 in high.
How much does a used conex box cost?
It depends on the size, the grade and how far the box travels. A used 20ft wind and watertight box is the least expensive option on our fixed national list. Enter your ZIP to see your delivered price.
Can a conex box be delivered to a residential driveway?
Usually, if the driveway gives the tilt-bed truck 60 to 100 ft of straight approach for a 20ft and there are no low wires over the drop spot. The truck slides the box straight off the back, so it can't lift it over a fence or around a corner.
Do conex boxes leak?
New, cargo-worthy and wind and watertight boxes are all watertight when inspected. Over the years, leaks can show up at the roof and door seals, and condensation forms inside in humid weather. Keep it level on a pad, add vents and check the roof once a year. Our wind and watertight warranty runs 5 years on used containers and 10 on new, from the delivery date.
Looking for a conex box? Give us your ZIP and the size and grade you want, and we'll send one delivered price. See my price takes about two minutes and doesn't commit you to anything.
