20ft vs 40ft vs 40HC: Container Sizes, Payload, Load Math

When you ship FCL, the choice between a 20ft, a 40ft and a 40HC (high cube) comes down to one question: will your cargo hit the volume limit or the weight limit first? This guide compares the three types using a carrier’s published specifications, shows how to choose by cargo density, and walks through two loading calculations.

Key takeaways

• Bottom line: a 40ft holds about 2.04× the volume of a 20ft (67.7 ÷ 33.2) and a 40HC about 1.13× a 40ft (76.3 ÷ 67.7), yet all three top out at around 28 tonnes of payload, so dense cargo suits a 20ft and light, bulky cargo a 40ft or 40HC.
• On published carrier specs (Hapag-Lloyd as the example), internal volume is 33.2 CBM for a 20ft, 67.7 CBM for a 40ft and 76.3 CBM for a 40HC.
• Max payload is similar across all three, at around 28 tonnes (20ft 28,130 kg, 40ft 28,750 kg, 40HC 28,600 kg). Dense cargo therefore suits a 20ft, while light, bulky cargo suits a 40ft or 40HC.
• A 40HC is 305 mm taller inside than a 40ft and holds about 8.6 CBM more. Actual specs vary by unit, so check the carrier’s sheet and the markings on the container you are given.

What are 20ft, 40ft and 40HC containers?

A 20ft container is the standard dry box, 6,058 mm (about 6 m) long outside, and is often used for dense cargo. A 40ft is 12,192 mm long, about twice the length, and is the most common choice for general cargo. A 40HC (high cube) has the same length and width as a 40ft but stands 9 ft 6 in (2,896 mm) tall outside, 1 ft (305 mm) more than the standard 8 ft 6 in (2,591 mm).

External dimensions and ratings such as max gross mass are set by ISO 668, and the ISO 1496 series is the reference for internal dimensions. Real internal sizes and tare weights differ slightly by manufacturer and carrier, so treat the figures below as one carrier’s published example and confirm with your own carrier before booking.

What are the sizes and weight limits?

The table shows Hapag-Lloyd’s published specifications for standard dry containers.

Dimensions and volume

Type	Inside L × W × H (mm)	Door height (mm)	Volume
20ft	5,900 × 2,352 × 2,395	2,292	33.2 CBM
40ft	12,032 × 2,352 × 2,395	2,292	67.7 CBM
40HC	12,032 × 2,350 × 2,700	2,597	76.3 CBM

Weight

Type	Max gross	Tare	Max payload
20ft	30,480 kg	2,350 kg	28,130 kg
40ft	32,500 kg	3,750 kg	28,750 kg
40HC	32,500 kg	3,900 kg	28,600 kg

Max payload can differ a lot between boxes of the same size. HM Global Logistics, for example, lists about 26,780 kg for a 40ft and about 26,580 kg for a 40HC, close to 2 tonnes less than the table above. For heavy cargo, check max payload before you book, then check again against the MAX GROSS and TARE markings on the door and the CSC safety approval plate of the container you receive.

How do you choose a container by cargo density?

Start by working out cargo density (total weight ÷ total volume, in kg/CBM). Dividing each type’s max payload by its volume gives the density at which, in theory, the box fills up by weight and volume at the same time.

Type	Max payload ÷ volume	What it means
20ft	about 847 kg/CBM	Denser cargo hits the weight limit first
40ft	about 425 kg/CBM	Lighter cargo runs out of space first
40HC	about 375 kg/CBM	The lighter and bulkier the cargo, the more the extra HC volume helps

Dense cargo such as machine parts, metal or tiles will hit the weight limit in a 40ft with space to spare, so a 20ft is usually more efficient. Light cargo fills the space first, so look at a 40ft or 40HC. For tall pallet stacks or tall items, the 40HC’s higher interior (2,700 mm) and door opening (2,597 mm) may be what you need.

These are theoretical figures. Carton sizes, pallet layout, orientation and clearance at the doors mean you rarely fill the full internal volume. Draw a load plan from your carton dimensions to see what really fits. How to calculate CBM is covered in CBM in logistics.

How do you calculate a load?

Example 1: light cartons

• 800 cartons, 0.06 CBM and 12 kg each
• Total volume = 800 × 0.06 = 48 CBM
• Total weight = 800 × 12 = 9,600 kg
• Density = 9,600 ÷ 48 = 200 kg/CBM (volume runs out first)

This does not fit in a 20ft (33.2 CBM). In a 40ft (67.7 CBM) it uses about 71% of the theoretical volume, and the weight is well within the limit. If it all fits in a 40ft there is no need for a 40HC, but carton height and stacking pattern can change the result, so confirm with a load plan.

Example 2: heavy machine parts

• Total volume 25 CBM, total weight 22,000 kg (22 tonnes)
• Density = 22,000 ÷ 25 = 880 kg/CBM (weight runs out first)

This fits within a 20ft’s 33.2 CBM and 28,130 kg max payload. Heavy cargo also needs a floor-load check: Hapag-Lloyd’s specification gives a maximum evenly spread load of 4.8 tonnes per running metre for 20ft containers. Spread evenly over the 5.9 m interior, 22 tonnes is about 3.7 tonnes per metre, which is within that limit, but concentrating it in one area can be a problem. For the VGM, declare the cargo’s 22,000 kg plus the 2,350 kg tare plus packing and lashing materials.

What are the common mistakes?

Most container mistakes come from planning on theoretical volume, confusing the 40ft with the 40HC, or getting the weight wrong. Each one can leave cargo behind or get the box refused.

• Planning on 100% of theoretical volume: carton sizes and layout mean less fits in practice, and cargo gets left behind.
• Mixing up a 40ft and a 40HC: the interior height difference (2,395 mm vs 2,700 mm) can leave tall cargo that does not fit and has to be reworked.
• Assuming every 40ft has the same max payload: max gross and tare vary by unit, and payload can differ by close to 2 tonnes.
• Getting the VGM wrong: a mis-declared gross mass can see the box refused for loading. See VGM meaning and submission.
• Forgetting the wooden pallets: if you use raw-wood pallets, check they meet ISPM 15 wood packaging rules.

Whether FCL or LCL makes more sense is covered in FCL vs LCL.

FAQ

How many CBM fit in a 20ft container?

Hapag-Lloyd’s specification gives an internal volume of 33.2 CBM. What you can actually load is less and depends on carton sizes and how you stack, so draw a load plan from your carton dimensions to be sure.

What is the difference between a 40HC and a 40ft?

Length and width are the same; the 40HC is 1 ft (305 mm) taller. On the same carrier’s specs, internal volume is 67.7 CBM for a 40ft and 76.3 CBM for a 40HC, about 8.6 CBM more, and the door opening rises from 2,292 mm to 2,597 mm.

How should I compare freight rates between container types?

There is no fixed ratio; the gap depends on carrier, trade lane and season. Get same-day quotes for each type, divide by what you can actually load, and add local charges, inland haulage and any demurrage and detention beyond free time.

Do I need to specify the container type when booking FCL?

Yes. You book a type such as 20GP, 40GP or 40HC. Equipment shortages can lead to substitutions, so if height or weight matters for your cargo, check the type again on the booking confirmation.

Sources

• ISO, ISO 668:2020 Series 1 freight containers — Classification, dimensions and ratings
• Hapag-Lloyd, 20’ Standard container specification
• Hapag-Lloyd, 40’ Standard container specification
• Hapag-Lloyd, 40’ Standard High Cube container specification
• Hapag-Lloyd, Container Specification (PDF, spread-load limits)
• HM Global Logistics, Container specifications (external dimensions, 40ft payload comparison)

Related: FCL vs LCL, VGM meaning and submission, Demurrage vs detention