The Container Buying Guide.
Everything you need to know before you buy a shipping container — new vs. used, grades, sizes, inspection, delivery, and the mistakes to avoid. Written by people who've delivered hundreds of them.
What Is a Shipping Container?
A shipping container (also called a "conex box" or "ISO container") is a standardized steel box used to move cargo around the world. The most common sizes are 20ft and 40ft, and they're built to a set of international standards — primarily ISO 668 and ISO 1496-1 [citation:1]. Because of these standards, any container built to spec can be stacked, lifted, and moved by any crane or truck anywhere in the world.
Standard dry containers (called "general purpose") have:
- Corrugated steel walls for structural strength
- A wooden or steel floor, often reinforced for forklifts
- Double doors at one end with locking bars
- Corner castings at all 8 corners for lifting and stacking
- A CSC plate certifying safety for transport (if cargo-worthy) [citation:1]
Containers come in three main sizes for the general market: 20ft, 40ft, and 40ft High Cube [citation:17].
Side note: There are also specialty containers — open-top, flat-rack, refrigerated, and tank — but those are for specialized cargo. Most buyers want a standard dry container.
New vs. Used — Which Should You Buy?
The single biggest decision in your container purchase is: new or used?
These have made exactly one trip from the factory to the depot. They're in essentially factory-fresh condition — no rust, no dents, no prior cargo.
Best for: Conversions (office, home, workshop), long-term storage, resale value.
Used containers come in grades. Every grading system is different, but the industry broadly recognizes four tiers — from IICL (near-new) down to As-Is (functional but rough).
Best for: Budget storage, export, or when cosmetic condition doesn't matter.
Here's the quick breakdown of used grades — we dive deeper in the next section:
| Grade | Age | Condition | Best For |
|---|---|---|---|
| IICL Multi-Trip | 3–5 years | Near-new, minor cosmetic wear | Conversions, long-term storage, resale |
| Cargo Worthy | 7–12 years | Structurally sound, CSC-certified | Export, functional storage |
| Wind & Watertight | 12+ years | Weather-tight, visible wear | Budget storage, non-shipping use |
| As-Is | Varies | Functional but cosmetically rough | Non-critical storage |
Container Grades Explained
IICL — The Best Used Grade
IICL stands for the Institute of International Container Lessors — the trade association for the container leasing industry. IICL containers have passed inspection against criteria designed to ensure the container is in good enough condition to ship cargo on a long-term basis [citation:8][citation:14].
IICL containers typically have original features intact, with only minor dings or dents. They're guaranteed wind and watertight, feature solid flooring, and have no structural issues [citation:8].
What to expect: Floors and walls intact but may show repair evidence. Forklift scratches on the floor are common. Superficial rust, dings, and dents. Solid structure, no leaks.
Cargo Worthy — For Shipping
Cargo Worthy (CW) means the container meets all original specifications and is suitable for transportation. It must meet WWT standards and pass structural requirements. CW containers with valid CSC plates are suitable for overseas transport [citation:1].
Unlike IICL, which is a global standard, Cargo Worthy standards can vary depending on the operator or region. But the basics are consistent: no holes, no large dents, strong floors, and safe to withstand transport forces [citation:14].
What to expect: Structurally sound, wind and watertight, valid CSC plate (if certified). Cosmetic wear is expected — scratches, minor dents, stained floors, patch repairs.
Wind & Watertight — For Storage
Wind & Watertight (WWT) means the container keeps weather out — when closed tight, you shouldn't see any light through the seams. It does not mean structurally sound for shipping [citation:1][citation:20].
WWT containers are the standard grade for storage use. They are not certified for cargo transport. They've typically spent 15–20 years at sea and show clear evidence of their journeys [citation:8].
What to expect: Doors seal properly, floors intact, no leaks. But significant dings, dents, and surface rust. Not stackable for shipping. Perfect for on-site storage.
Important: There is no universal grading system. A "Grade A" from one seller isn't necessarily equivalent to a "Grade A" from another. Always ask what standard (IICL, CW, WWT) applies [citation:20].
Sizes & Specifications
| Feature | 20ft Standard | 40ft Standard | 40ft High Cube |
|---|---|---|---|
| External Length | 6.06 m (19.9 ft) | 12.19 m (40 ft) | 12.19 m (40 ft) |
| Internal Length | ~5.90 m (19.4 ft) | ~12.03 m (39.5 ft) | ~12.03 m (39.5 ft) |
| Internal Width | ~2.35 m (7.7 ft) | ~2.35 m (7.7 ft) | ~2.35 m (7.7 ft) |
| Internal Height | ~2.39 m (7.8 ft) | ~2.39 m (7.8 ft) | ~2.69 m (8.8 ft) |
| Volume | ~33 m³ (1,165 ft³) | ~67 m³ (2,366 ft³) | ~76 m³ (2,684 ft³) |
| Tare Weight | ~2,200–2,300 kg | ~3,700–3,800 kg | ~3,900–4,000 kg |
| Max Payload | ~28,000 kg | ~26,500–27,000 kg | ~26,000–29,000 kg |
| Pallet Capacity | 10–11 | 21–25 | 21–25 |
Data sourced from multiple carriers including Hapag-Lloyd; actual dimensions vary slightly by manufacturer [citation:4][citation:5][citation:9].
The counterintuitive part: A 40ft container holds double the volume of a 20ft, but its payload capacity is often lower. That's because the container itself is heavier. If you're shipping dense, heavy cargo, a 20ft may let you pack more total weight [citation:16].
Which Size Do You Need?
- 20ft — Heavy, dense items. Small yards. Simpler delivery.
- 40ft — Bulky, lighter items. Maximum storage. Conversions.
- 40ft HC — Same footprint, extra foot of height. Tall equipment, conversions.
What to Inspect Before Buying
If you're buying used, never buy sight-unseen without photos. Here's what to check:
Structure
- Any visible holes or perforations in walls, roof, or floor
- Large dents in side panels or corner posts
- Door alignment — do they close flush and seal?
- Floor integrity — soft spots, delamination, rot
Weather-Tightness
- Look inside with doors closed and lights off — any daylight means a leak
- Check the roof for pinholes or rust-through
- Inspect door gaskets for cracks or compression
Certification
- Ask to see the CSC plate if you need cargo-worthy [citation:1]
- Verify the plate is current (containers over 5 years old need regular inspection for CW status) [citation:1]
Cosmetics (Expected)
- Surface rust, dents, scratches, faded paint are normal on used containers
- These are not defects — they're part of the grade
Delivery & Site Preparation
How Containers Arrive
Containers are delivered by tilt-bed or hiab (boom) truck, depending on your site access and container size [citation:8]. The driver will place the container as close to your desired spot as safely possible.
Site Requirements
- Space: A 20ft needs about 25 ft of straight access; a 40ft needs about 50 ft
- Ground: Firm and level — containers should sit on blocks, pavers, or a gravel pad
- Obstructions: No low wires, branches, or overhangs on the delivery route
- Approval: Check HOA rules and local permits if required
Placement
Standard delivery includes placement at a location the driver can safely reach. If your drop is tricky (tight corner, over a fence), discuss it with the seller in advance — extra placement fees may apply.
Pro tip: Send a photo of your access route to the seller before buying. A 30-second photo can prevent a failed delivery and a refund headache.
Common Mistakes to Avoid
Buying the wrong grade
Don't buy WWT if you need to ship cargo. Don't buy new if you just need a storage box.
Skipping the CSC plate check
If it's going on a ship, it needs a valid CSC plate [citation:1].
Not verifying site access
A container that can't be delivered is a refund headache. Send a photo of your access route to the seller before buying.
Assuming "used" means "bad"
A properly graded used container can easily last 15–20 years with basic care.
Forgetting about foundations
Containers should not sit directly on dirt. Use blocks, sleepers, or gravel.
Not asking about delivery cost upfront
Delivery is often 30–50% of the total cost. Get it in writing.
After You Buy — Maintenance
- Touch up scratches with marine-grade paint to prevent rust spread
- Keep the roof clear of standing water and debris
- Ventilate to reduce internal condensation
- Check door seals annually
- Re-level if the container settles unevenly
With basic care, a quality container can serve you for 20+ years.
We'll help you pick the right container.
Tell us what you're storing or shipping, and we'll recommend the right size and grade — no pressure, no upsell. Just a straight answer.