Quick Answer: Conex Box
A conex box is a steel shipping container bought or rented for storage, job sites, farms or conversion into an office. Most are 20ft or 40ft long and 8ft wide. A used 20ft costs about $1,200–$2,800 and a new one-trip 20ft $2,500–$5,000; a used 40ft runs $1,800–$3,500 and a new 40ft $3,500–$6,500. Delivery adds $300–$2,500+ by distance, and renting costs $75–$200 a month for a 20ft or $100–$300 for a 40ft.
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Conex Box: What It Is, Sizes, Grades and Prices
A conex box is the everyday name for a steel shipping container used on land. People buy them to lock up tools on a job site, store feed and equipment on a farm, or clear out a garage. Prices look simple until you notice that one seller's "used" is another seller's "as-is."
This page is for anyone about to buy or rent one. It covers what the name means, the standard sizes, how condition grades work, what each size and grade costs, and when renting beats buying. It also covers delivery, the ground the box sits on, permits, and what to check before you pay.
What Is a Conex Box?
A conex box is a steel intermodal shipping container, the same kind that rides on ships, trains and trucks. Once it leaves freight service, it gets a second life as secure, weather-tight storage. Buyers call it a conex container, a storage container or a shipping container. They all mean the same steel box.
The name is older than the modern container. CONEX was short for Container Express, a steel container system the U.S. Army Transportation Corps developed during the Korean War to cut breakage and theft at ports, according to GlobalSecurity.org's history of military containers. The Army name stuck. Today it covers any steel box of this type.
Modern containers are built to ISO standards, and their standard sizes are set by ISO 668. That is why a 20ft unit from one supplier has the same outside footprint as a 20ft unit from another. The inside is a different story. Interior sizes, empty weights and payloads vary by manufacturer, so treat any interior figure as typical rather than exact.
What makes a conex box useful is simple. It arrives with a steel frame, floor, walls, roof and lockable cargo doors already in place. There is nothing to assemble. What it lacks out of the box is insulation, power, windows and, for most uses beyond storage, approval from your local building department.
Conex Box Sizes and Dimensions
Two lengths make up most of the market: 20 feet and 40 feet. Both are 8 feet wide. A standard container is 8'6" tall on the outside, and a high cube adds a foot for 9'6". Ten-foot and 45-foot units exist too, but they are less common and priced by the unit.
| Size | Exterior (L x W x H) | Typical Interior (L x W x H) | Typical Door Opening | Footprint | Typical Empty Weight |
|---|---|---|---|---|---|
| 20ft standard | 20' x 8' x 8'6" | 19'4" x 7'8" x 7'10" | 7'6" W x 7'5" H | 160 sq ft | about 4,850 lbs |
| 40ft standard | 40' x 8' x 8'6" | 39'5" x 7'8" x 7'10" | 7'6" W x 7'5" H | 320 sq ft | about 8,160 lbs |
| 40ft high cube | 40' x 8' x 9'6" | 39'5" x 7'8" x 8'10" | 7'6" W x 8'5" H | 320 sq ft | about 8,510 lbs |
Exterior figures are the standard sizes. Interior sizes, door openings and weights are typical and vary by manufacturer, so check the unit you are buying. The door opening is the number that catches people out. Anything wider than the doors will not go in, however much floor space sits behind them.
Measure What You Plan to Store
Before choosing between conex box sizes, measure your largest item against the door opening and the interior height. A mower deck, a pallet stack or a tall shelving unit can decide the size for you.
A 20ft unit suits tools, seasonal stock or the contents of a house during a move. It also fits more easily on a tight lot. A 40ft unit gives you twice the floor area and is usually better value per square foot when your site can take the length. Pick a high cube when people will work inside, or when tall items need that extra foot. The 20ft container guide and the 40ft and high cube guide go deeper on each size.
Container Grades: One-Trip to As-Is
Condition moves the price more than anything except size. Grade names are not policed the same way by every seller, so ask what each label means before you compare quotes. These are the grades you will usually see.
- New (one-trip): built for export and used for a single loaded trip, then sold. The best choice for conversions and customer-facing use.
- IICL / multi-trip: a used grade priced between new and cargo-worthy. Ask the seller what inspection it passed.
- Cargo-worthy: inspected and certified to carry cargo. It can still show dents, surface rust and worn paint.
- Wind and watertight: sealed against weather but not certified for shipping. A common choice for ground-level storage.
- As-is: sold in its current condition, with no repairs or guarantees. It may leak.
For storage on your own land, wind and watertight is often enough. You are paying for a box that keeps rain out, not one that crosses an ocean. Cargo-worthy matters if the container might ever carry freight again. It also offers some reassurance about structural condition.
New one-trip units cost more but have clean walls, sound floors and doors that close easily. That matters if you plan to cut in a window, insulate or put customers inside. Paying for a cheaper grade and then fixing rust and floors can erase the saving quickly.
As-Is Means As-Is
An as-is container can have holes, soft floorboards or doors that will not seal. Only buy one when you have seen it, or when you plan heavy modification that replaces the damaged parts anyway.
Conex Box Prices by Size and Grade
The table below uses this site's purchase figures for each common size and grade. Your conex box price will land higher or lower within each range depending on how close you are to a container depot and how much stock is nearby.
| Grade | 20ft Standard | 40ft Standard | 40ft High Cube |
|---|---|---|---|
| New (one-trip) | $2,500–$5,000 | $3,500–$6,500 | $4,000–$7,000 |
| IICL / multi-trip | $2,000–$3,500 | $2,800–$4,500 | Used: $2,200–$3,800 |
| Cargo-worthy | $1,500–$2,800 | $2,000–$3,500 | |
| Wind and watertight | $1,200–$2,200 | $1,800–$2,800 | |
| As-is | $800–$1,500 | $1,000–$2,000 | Quoted by condition |
| Delivery (purchase) | $300–$2,500+ by distance from the nearest depot | ||
Delivery is quoted separately and can match the cost of a cheap box on a long haul. Always ask for the delivered price. A 10ft or 45ft container is quoted by size, condition and location, because far fewer of them trade.
A 40ft container costs more than a 20ft, but not twice as much. If you need more than about 160 square feet, one 40ft unit is usually cheaper than two 20ft units. It also gives you one long room rather than two separate boxes. The full breakdown by grade lives on the shipping container prices guide.
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Renting vs Buying a Conex Container
Renting a conex box makes sense for a short project, such as a remodel, a move or a construction job. Buying makes sense when the container will stay for years. The gap between the two narrows faster than most people expect.
Rental rates run $75–$200 a month for a 20ft and $100–$300 a month for a 40ft. Rental delivery costs $150–$500, and pickup at the end costs about the same. Purchase delivery runs $300–$2,500+, but you only pay it once and you keep the box.
Worked Example: One 20ft Container for 12 Months
Renting: $75–$200 a month x 12 = $900–$2,400.
Rental delivery: $150–$500.
Rental pickup: $150–$500.
Total to rent for a year: $1,200–$3,400.
Buying wind and watertight: $1,200–$2,200.
Purchase delivery: $300–$2,500+.
Total to buy: $1,500–$4,700+.
This is an example built from the ranges on this page, not a quote. After a year the renter has spent a similar sum and owns nothing. The buyer still has a container to use or sell.
If your need is measured in weeks, rent. If it runs well past a year, buying usually wins. Rental terms, minimums and damage waivers vary by supplier, so compare the full cost rather than the monthly rate. The storage container rental cost guide works through rental terms and the break-even in detail.
What Conex Containers Are Used For
Most conex boxes never get modified. They sit on a gravel pad and hold things. That is the use they suit best, because a lock, steel walls and a watertight roof are all you need.
Storage on Farms, Job Sites and Homes
Farms use them for feed, fencing supplies and small equipment. Contractors use them as lockable tool rooms that move from site to site. Homeowners use them during a remodel or a move, or as a long-term shed. Businesses use them for overflow stock. For these jobs, a used wind and watertight or cargo-worthy conex box is usually the right grade.
Bare steel can collect condensation inside when warm, damp air meets a cold wall. Vents, a little airflow and keeping stored items off the floor help. Paper, fabric and anything that rusts need more care than tools and bins.
Offices, Homes and Cabins
Once people work or live inside, a container becomes a building project. It needs openings, insulation, power, often heating and cooling, and a permit. This site's office figures put a basic conversion at $10,000–$20,000 for a 20ft and $18,000–$30,000 for a 40ft. Mid-range builds run $20,000–$40,000 and $30,000–$55,000. Premium builds reach $35,000–$60,000 for a 20ft and $50,000–$75,000+ for a 40ft.
The shipping container office guide breaks those tiers down. Homes and cabins are quoted by design, finish and site, and are covered in the container home guide and the container cabin guide.
When a Steel Building Is the Better Buy
A container is 8 feet wide, and joining several of them adds cutting, reinforcement and engineering. Once you need a wide open room, a shop with vehicle doors or a large footprint, a pre-engineered steel building is usually the better value. The Metal Building Manufacturers Association represents that industry, and the container vs metal building comparison sets the two side by side.
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Delivery, Ground Prep and Permits
Most delivery trucks tilt the bed and slide the container off, so they need a long, straight and level approach. Overhead wires and branches matter as much as length. Ask the supplier for the clearance their truck needs, and walk the route before delivery day. A 40ft unit needs far more room than a 20ft.
Where a truck cannot reach, a crane can set the conex box instead. Crane work is quoted by the job. Lifting a load that heavy is skilled work with real crush hazards, and OSHA's cranes and derricks guidance notes the safety issues for both operators and anyone standing nearby. Keep people clear during the lift.
The ground matters more than people think. A container that sits out of level can twist enough that the doors bind. Firm, level gravel or solid blocks under the corners work for most storage. Soft ground, a slope or a long-term install may call for a proper pad or footings.
Permits are local. Placing a container on your property usually needs zoning approval, and it often needs a permit, especially for anything beyond storage. Setbacks, placement and appearance rules vary by town and county. Call your planning or building department before you order.
Using a container as a building brings in the building code. The International Code Council's G5 guideline for shipping containers repurposed as buildings exists to help jurisdictions, owners, builders and engineers assess how to design, review and approve containers as building elements. The metal building permits and codes guide explains the general permit process.
How to Inspect a Used Container Before You Buy
Photos hide a lot, and a used conex box can look better in a picture than in person. See the container in person if you can, or ask for recent photos of the specific unit, not a stock picture. Then work through the same checks a careful buyer makes.
- Doors and seals: both doors should open, close and lock without force, with rubber seals intact.
- Light test: step inside, close the doors and look for daylight through the walls or roof.
- Floor: walk the whole floor and feel for soft, delaminated or patched boards.
- Roof: look for dents that hold standing water, which leads to rust.
- Rust: surface rust can be treated; rust that has eaten through the steel cannot.
- Paperwork: ask for the grade in writing, and proof of certification if you are paying for cargo-worthy.
Plan any modification before you buy. The corrugated walls and frame work together, so cutting a large opening removes steel the box relies on. How much reinforcement an opening needs is an engineer's call. Cutting steel also brings fire and fume hazards, which are covered by OSHA's welding, cutting and brazing standards.
Don't Cut First and Ask Later
A roll-up door or a row of windows can weaken a container more than it looks. Get the openings designed before cutting, and hire someone who does structural steel work for the cuts and framing.
Frequently Asked Questions
A conex box is a steel shipping container used on land for storage, job-site lockup or conversion into an office or other space. The terms conex container, storage container and shipping container all describe the same kind of steel box.
CONEX was short for Container Express, a steel container system the U.S. Army Transportation Corps developed during the Korean War. The name outlived the program and is now used for steel shipping containers in general.
A used 20ft costs about $1,200–$2,800 and a new one-trip 20ft $2,500–$5,000. A used 40ft standard runs $1,800–$3,500 and a new one $3,500–$6,500. Delivery adds $300–$2,500+ depending on distance from the nearest depot.
The common sizes are 20ft and 40ft long, both 8ft wide. Standard units are 8'6" tall outside and high cubes are 9'6". Ten-foot and 45-foot units exist but are less common. Interior sizes vary by manufacturer.
A cargo-worthy container has been inspected and certified to carry cargo. A wind and watertight container is sealed against weather but not certified for shipping. For storage on your own land, wind and watertight is often enough.
Renting is cheaper for short projects. A 20ft rents for $75–$200 a month and a 40ft for $100–$300, plus delivery and pickup. If you need the container for well over a year, buying usually costs less, and you keep the box.
Usually you need zoning approval, and often a permit, especially if people will use it as an office, workshop or living space. Rules are set locally, so check with your planning or building department before the container is delivered.
A 20ft standard typically weighs about 4,850 lbs empty, a 40ft standard about 8,160 lbs and a 40ft high cube about 8,510 lbs. Empty weights vary by manufacturer, so check the specification for the unit you buy.
It needs firm, level support so the frame stays square and the doors keep working. Compacted gravel or solid blocks under the corners suit most storage use. Soft ground, slopes and permanent buildings may need a pad or footings.
Yes. A basic office conversion runs about $10,000–$20,000 for a 20ft and $18,000–$30,000 for a 40ft, with mid-range and premium builds costing more. It needs insulation, power and usually a permit, and cutting openings should be designed by an engineer.
Choosing the Right Container
Start with the job the conex box has to do. For storage, a used wind and watertight or cargo-worthy unit in the right length is usually all you need. For an office or anything people use daily, start with a new one-trip high cube and budget for the conversion. Either way, check the zoning and the delivery route first.
Then compare delivered prices from more than one supplier. Grade names and delivery charges vary enough that the cheapest box on paper is not always the cheapest one on your land. A few quotes will show you the real price.
Related Resources
- Shipping Container Prices: Costs by Size and Grade
- 20ft Shipping Container Cost: Sizes and Pricing
- 40ft Shipping Container Cost: Standard and High Cube
- Storage Container Rental Cost: Monthly Rates and Delivery
- Shipping Container vs Metal Building: Which to Choose
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