Container types: dimensions, payloads and when to use each
Updated
Choosing a container means trading off three limits: length, volume and weight. Pick wrong and you pay for an avoidable second box, ship a half-empty one — or discover at stuffing time that a crate doesn't clear the door.
Here are the common types with interior dimensions in millimetres and payloads, as used by ALPHA LOADING's presets (sourced from Maersk / Hapag-Lloyd). One caveat worth repeating: interior dimensions vary by ±10 to ±30 mm between manufacturers and series, even for the same ISO type — for millimetre-tight loads, check the actual box you're allocated.
The reference table
| Type | Int. L (mm) | Int. W (mm) | Int. H (mm) | Computed vol. | Door W × H (mm) | Payload |
|---|---|---|---|---|---|---|
| 20ft Dry | 5,896 | 2,350 | 2,393 | ≈ 33.2 m³ | 2,350 × 2,274 | 28,200 kg |
| 40ft Dry | 12,032 | 2,350 | 2,393 | ≈ 67.7 m³ | 2,340 × 2,274 | 28,800 kg |
| 40ft High Cube | 12,032 | 2,350 | 2,697 | ≈ 76.3 m³ | 2,340 × 2,577 | 28,620 kg |
| 45ft High Cube | 13,556 | 2,352 | 2,698 | ≈ 86.0 m³ | 2,340 × 2,585 | 27,600 kg |
| 20ft Open Top | 5,888 | 2,345 | 2,315 | ≈ 32.0 m³ | 2,338 × 2,234 | 28,120 kg |
| 40ft Open Top | 12,028 | 2,344 | 2,326 | ≈ 65.6 m³ | 2,335 × 2,263 | 26,630 kg |
| 20ft Flat Rack | 5,940 | 2,345 | 2,245 | — | n/a | 30,140 kg |
| 20ft Reefer | 5,449 | 2,290 | 2,244 | ≈ 28.0 m³ | 2,290 × 2,264 | 27,450 kg |
| 40ft HC Reefer | 11,583 | 2,290 | 2,544 | ≈ 67.5 m³ | 2,290 × 2,478 | 29,520 kg |
20ft or 40ft: the weight-vs-volume rule
The most important fact in that table is counter-intuitive: a 40ft does not carry twice a 20ft — 28,800 kg versus 28,200 kg, nearly identical. Two 20ft boxes therefore carry 56,400 kg where one 40ft caps at 28,800 kg, often for similar freight rates.
The decision rule: above roughly 850 kg/m³ of density, a 20ft fills up on weight before it's full on volume — it's the box for dense freight (metal, tiles, beverages, paper). The 40ft and 40ft HC fill up on volume — the boxes for light, bulky freight (furniture, textiles, plastics). Running that calculation is precisely what CBM is for — traps included.
High Cube and 45ft: buying height or length
The 40ft High Cube offers the same 12,032 mm length as the 40ft Dry but 2,697 mm of ceiling height (+304 mm): ≈ 76.3 m³ versus 67.7 m³ — nearly 13% more volume for practically the same payload. It has become the de facto standard for bulky imports: if your freight stacks above 2.4 m, the HC pays for itself.
The 45ft High Cube adds length (13,556 mm) and reaches ≈ 86 m³. Its niche is light, voluminous freight on intra-European and transatlantic lanes — at the price of slightly lower payload (27,600 kg) and patchier availability depending on the trade.
Reefer: the dimensions trap
A refrigerated container carries its cooling unit and insulation inside the ISO envelope: a 20ft Reefer offers only 5,449 × 2,290 × 2,244 mm — about 45 cm less length and 15 cm less height than a 20ft Dry. This is THE classic quoting mistake: a load computed against dry-box dimensions simply no longer fits.
Cold freight also has its own stuffing rules: never block the T-bar floor, and preserve the air circulation space at the top — cargo must never rise above the max load line marked inside the box. Refrigeration only works if air can flow around the goods.
Open top and flat rack: out-of-gauge territory
The open top swaps the roof for a tarpaulin and loads from above by crane — machinery, glass, coils, tall pieces. Interior dimensions stay close to a dry box (5,888 × 2,345 × 2,315 mm for a 20ft), the height being measured to the tarpaulin line; taller cargo travels uncovered as out-of-gauge.
The flat rack has no roof and no side walls: a reinforced floor and two end walls. It's the platform for genuinely over-width and concentrated heavy cargo — payload reaches 30,140 kg on our 20ft preset. The trade-off: with no walls, all securing is the shipper's job (lashings, timber blocking), and conventional stacking logic no longer applies.
Which box for which freight?
In every case, the final call isn't made on cubic metres but on a load plan: the proof that crates clear the door, weight is distributed, and nothing gets left on the dock.
- Dense freight (> ~850 kg/m³: metal, tiles, beverages) → 20ft Dry, often several. Weight saturates before volume.
- Light, bulky freight (furniture, textiles, e-commerce) → 40ft High Cube by default; 45ft HC where available and volume rules.
- Standard palletised cargo → 20ft or 40ft Dry; expect about 11 Euro pallets on the floor in a 20ft and 25 in a 40ft (single-stacked, on our presets).
- Temperature-controlled → Reefer — and recompute EVERYTHING with reefer dimensions, not dry ones.
- Too tall for the door, but craneable → Open top.
- Too wide, too heavy, indivisible → Flat rack, with a dedicated securing plan.
Frequently asked questions
- What are the interior dimensions of a 20ft container?
- On our presets (sourced from Maersk / Hapag-Lloyd): 5,896 × 2,350 × 2,393 mm, door opening 2,350 × 2,274 mm, payload 28,200 kg — about 33 m³. Dimensions vary ±10–30 mm between manufacturers.
- What's the difference between a 40ft Dry and a 40ft High Cube?
- Same length and width (12,032 × 2,350 mm) but 2,697 mm of interior height on the HC versus 2,393 mm on the Dry: roughly 76 m³ versus 68 m³, for nearly identical payloads (28,620 kg vs 28,800 kg).
- Does a 40ft container carry twice as much as a 20ft?
- No — that's the classic trap. A 40ft Dry carries 28,800 kg, barely more than a 20ft's 28,200 kg. For dense freight, two 20ft boxes (56,400 kg combined) beat one 40ft.
- Why is a reefer smaller than a dry container?
- The cooling unit and insulation live inside the standard ISO envelope, so they're paid for in interior space. A 20ft Reefer loses about 45 cm of length and 15 cm of height versus a 20ft Dry — any quote made with dry dimensions is wrong.