What Is a Conex Box?
A conex box is a steel intermodal shipping container manufactured to the dimensional standards set by the International Organization for Standardization (ISO). The word “conex” is short for “Container Express,” a shipping system first used by the U.S. military to move supplies. Today the term is used interchangeably with “shipping container,” “sea container,” “cargo container,” and “ISO container.”
Because conex boxes are built to intermodal standards, they are engineered to stack and lock uniformly on ships, rail cars, and chassis trailers. That standardization is the reason a container purchased in one region fits handling equipment anywhere in the world.
Conex Box vs. Shipping Container: Is There a Difference?
There is no structural difference. “Conex box” and “shipping container” describe the same product. The distinction is regional and historical: conex carries a North American, military-origin flavor, while shipping container and ISO container are the more technical, globally used terms. When buying, treat the words as synonyms and focus on size, condition, and configuration instead of terminology.
Conex Box Sizes and Standard Dimensions
Conex boxes are sold in a small number of standardized footprints. The table below summarizes the most common purchase options and their approximate specifications.
| Size | Exterior Length | Width | Height | Notes |
| 10-foot | 10 ft | 8 ft | 8.6 ft | Compact footprint for tight sites and smaller storage loads |
| 20-foot (standard) | 20 ft | 8 ft | 8.6 ft | The most common ISO size; interior ~19’4″ × 7’9″ × 7’10” |
| 40-foot (standard) | 40 ft | 8 ft | 8.6 ft | ~8,000 lbs; maximum floor space in a standard height |
| 40-foot high cube | 40 ft | 8 ft | 9.5 ft | Extra foot of interior height for tall |
New vs. Used Conex Boxes: Which Should You Buy?
The new-versus-used decision usually comes down to budget and intended use. Both are viable; the right choice depends on how visible, how permanent, and how specialized the container needs to be.
| Factor | New (One-Trip) Conex | Used Conex |
| Cost | Higher | Lower — the value option for storage |
| Cosmetic condition | Cleanest, most uniform | Shows prior cargo use |
| Best for | Offices, customer-facing builds, long-term installs | General storage, job-site use, budget projects |
| Resale/rental potential | Strong | Still resellable or rentable long-term |
Conex Box Types and Configurations
Beyond the plain “dry” box, conex containers can be purchased in specialized configurations. Matching the configuration to the job is the single biggest driver of long-term satisfaction with the purchase.
- Standard (cargo-door) containers — the baseline box with double doors on one end.
- Roll-up door containers — swap swing doors for an overhead roll-up for easier access; available in 10, 20, and 40-foot with single or multiple doors.
- Open-side / full-side-open containers — doors that open the full length of one side for wide loading.
- Office containers — insulated, finished interiors with electrical packages and marine plywood flooring, in layouts like 10′ guard shack, 20′ open bay, 20′ half office/half storage, and 40′ configurations.
- Refrigerated containers — insulated units with a temperature-controlled interior for cold or climate-sensitive goods.
- Insulated containers — lined for temperature moderation without full refrigeration.
- Custom builds — concession stands, car storage, event containers, guard shacks, and other made-to-spec solutions.
How to Evaluate a Conex Box Before Buying
A simple, repeatable evaluation framework helps buyers compare options on the same terms rather than reacting to price alone.
- Define the primary use. Storage, workspace, cold storage, and retail each point to a different configuration.
- Confirm the footprint. Measure the placement site and match it to a 10, 20, or 40-foot length before committing.
- Choose height. Standard (8.6 ft) suits most uses; high cube (9.5 ft) helps when racking tall items or installing interior fixtures.
- Set condition expectations. Decide whether a used box meets the need or whether a new, one-trip unit is warranted.
- Specify door and access needs. Cargo, roll-up, or full-side-open changes how easily you load and unload.
- List modifications up front. Vents, lockboxes, windows, insulation, and electrical are cheaper to plan than to retrofit.
Buy vs. Rent: How to Decide
Buying makes sense for permanent storage, ongoing operations, and any container you’ll modify. Renting fits temporary projects, seasonal overflow, and situations where you’d rather not own the asset. Aztec Container offers sales nationwide and rentals in California, so the same catalog can be approached either way depending on the project’s timeline.
Common Uses for a Conex Box
Conex boxes are bought by a wide range of buyers because the same steel shell adapts to many jobs:
- On-site storage for construction and job sites
- Inventory and equipment storage for retail, restaurants, and automotive shops
- Portable offices, guard shacks, and break rooms
- Refrigerated or insulated storage for temperature-sensitive goods
- Agricultural and industrial storage
- Custom concession stands, event spaces, and container structures
What Determines the Price of a Conex Box?
There is no single sticker price for a conex box. Cost is shaped by a combination of variables, and understanding them helps buyers compare quotes accurately:
- Size — 10, 20, 40-foot, or high cube.
- Condition — new/one-trip units cost more than used.
- Configuration — office, refrigerated, and open-side builds carry more than a standard dry box.
- Modifications — added doors, windows, vents, insulation, lockboxes, and electrical packages.
- Market conditions — availability and regional demand move pricing over time.
Because these factors stack, the most reliable way to price a specific build is a direct quote rather than a generic estimate.
Buying a Conex Box from Aztec Container
Aztec Container has built and supplied steel ISO shipping containers, storage containers, custom office containers, and conex box sea containers since 1969. Our company offers new and used units across the standard 10, 20, and 40-foot sizes, plus refrigerated, insulated, office, and fully custom configurations. Pricing is quoted up front and transparent, and Aztec is a member of the NPSA (National Portable Storage Association).
To price a specific conex box, call 1-800-399-2126 or request a quote through azteccontainer.com.
Frequently Asked Questions
What exactly is a conex box?
It’s a steel shipping container built to ISO standards. “Conex” is short for “Container Express,” a term that came out of U.S. military logistics. In everyday use, a conex box is the same thing people call a shipping container, sea container, or cargo container.
Is a conex box the same as a shipping container?
Yes. There’s no structural difference — the two names describe the identical product. “Conex” is just a more regional, military-rooted way of saying “shipping container,” so you can use the terms interchangeably when you shop.
What sizes can I buy a conex box in?
The standard purchase sizes are 10-foot, 20-foot, and 40-foot. There’s also a 40-foot high cube that adds about a foot of interior height. If your project needs something outside those, custom builds are available in 10, 20, 40, and 45-foot lengths.
What are the dimensions of a 20-foot conex box?
A standard 20-foot container is about 8 feet wide and 8.6 feet tall on the outside, with roughly 19’4″ × 7’9″ × 7’10” of interior space. It’s the most common size worldwide and the baseline the industry measures capacity by (the TEU).
How much does a 40-foot conex box weigh?
A standard 40-foot container weighs approximately 8,000 lbs empty. That’s worth knowing early, since the weight affects the ground and equipment needed to place it once it’s on your site.
Should I buy a new or used conex box?
It depends on your use. Used boxes are the value pick for general storage and job-site work and are still strong and resellable. New (one-trip) units are cleaner and more uniform, which makes them a better fit for offices or anything customer-facing.
Can a conex box be turned into an office?
Yes. Office conex boxes come insulated and finished with electrical packages and marine plywood flooring, in layouts like a 10′ guard shack, 20′ open bay, or 20′ half office/half storage. You can spec the floor plan to match how you’ll actually use the space.
What’s the difference between a standard and a high cube conex box?
Footprint is the same width and length — the difference is height. A standard box is about 8.6 feet tall on the outside, while a high cube is about 9.5 feet. That extra foot helps when you’re installing racking or storing tall equipment.
Do I have to buy, or can I rent a conex box?
Both are options. Buying suits permanent storage and anything you plan to modify; renting fits temporary or seasonal needs. Aztec Container sells nationwide and rents in California, so you can approach the same catalog either way.
What determines the price of a conex box?
Price comes from a mix of factors: size, whether it’s new or used, the configuration (office, refrigerated, open-side, etc.), and any modifications like extra doors, windows, or insulation. Market conditions also move pricing, so a direct quote is the most accurate way to price a specific build.