Volume or weight — which fills first.

Written by Efe Kamış · Co-founder
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Last updated
Basis ISO 668 · Hapag-Lloyd equipment specification
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Choosing a container is not a question of volume but of which limit fills first — cubic capacity or payload. A 20' box only hits its weight limit once your cargo exceeds 910 kg/m³; in a 40' High Cube that threshold is just 375 kg/m³. That is why marble, ceramics and canned goods go in 20-footers: the 40' is larger yet carries fewer tonnes.

Dimension table

The figures below come from Hapag-Lloyd's own published equipment specification, wooden-floor standard series. We name the source because, as explained below, these values differ between carriers and between build series; there is no such thing as a universal container table.

← Scroll the table →

Dry containers — Hapag-Lloyd wooden-floor standard series, dimensions in mm
TypeISO code Int. lengthInt. widthInt. height Door widthDoor height Max grossTareMax payloadCapacity
20' GP22G15,9002,3522,3932,3402,292 32,500 kg2,300 kg30,200 kg33.2 m³
40' GP42G112,0322,3522,3952,3402,292 32,500 kg3,700 kg28,800 kg67.7 m³
40' HC45G112,0322,4322,7002,3402,597 32,500 kg3,850 kg28,650 kg76.3 m³
45' HCL5G113,5562,3522,7002,3402,597 32,500 kg4,700 kg27,800 kg86.0 m³
20' Reefer22R15,4502,2842,2672,2902,264 30,480 kg2,905 kg27,575 kg28.2 m³
40' HC Reefer45R111,5782,2802,5252,2762,535 34,000 kg4,300 kg29,700 kg66.7 m³

External dimensions are standardised in ISO 668 — 6,058 mm for a 20', 12,192 mm for a 40', 13,716 mm for a 45'; heights 2,438 mm (standard), 2,591 mm (8'6") and 2,896 mm (9'6"). Internal dimensions are not. Hapag-Lloyd calls its own figures "nominal" and notes that production tolerances allow variation; the maximum difference ISO 668 permits is 10 mm in length, width and height. The texts of ISO 668 and ISO 6346 are paid publications; only the standard numbers are cited here.

The density threshold

Every container has two limits — capacity and payload — and which one you hit depends on the density of your cargo. The threshold is a simple division: max payload ÷ capacity.

Density thresholds by container type A horizontal density axis showing the threshold for six container types: 45 foot High Cube 323, 40 foot High Cube 375, 40 foot standard 425, 40 foot High Cube reefer 445, 20 foot standard 910 and 20 foot reefer 978 kilograms per cubic metre. Below the threshold volume fills first; above it the weight limit is reached first. 0200400 6008001000 cargo density — kg/m³ 45' HC · 323 40' HC · 375 40' GP · 425 40' HC reefer · 445 20' GP · 910 20' reefer · 978 ← volume fills first weight limit reached →
The gap between a 20' and a 40' is more than twofold. A 20' works on volume up to 910 kg/m³; a 40' HC hits weight at 375. So at a density of 500 kg/m³ most of a 40' HC's capacity goes unused, because the weight is already spent. These thresholds assume perfect stowage; real loading never reaches that fill rate once packaging, pallets and voids are accounted for. The threshold is a ceiling, not a target.

Decision rule

Work out your cargo's density: total kg ÷ total m³. Below 400 kg/m³ volume governs and a larger box makes sense. Above 900 kg/m³ weight governs and two 20-footers carry more than one 40-footer (2 × 30,200 = 60,400 kg against 28,650 kg in a 40' HC). In between, price both scenarios.

There is no rule against using a 40' for heavy cargo — but know you are paying for capacity you cannot use. A 40' HC is 76.3 m³, yet 28.6 tonnes of dense cargo typically occupies 30–40 m³. You pay freight on the rest.

Why published tables disagree

Container tables you find online contradict each other, and that is not an error — the containers genuinely differ. Even the single document we used as our source publishes more than one value for the same type:

  • Floor material. The same 20' GP has a 2,300 kg tare with a wooden floor and 2,250 kg with a steel floor. Change the tare and the payload changes with it.
  • Build series. In the same document one 20' GP series has a maximum gross of 32,500 kg while another has 30,480 kg — payload falls from 30,200 kg to 28,180 kg. Two tonnes of difference, purely on which series is allocated.
  • Production tolerance. The carrier calls its own figures nominal; ISO 668 permits up to 10 mm of variation in length, width and height.
  • Carrier differences. All of the above is variation within a single carrier. Between carriers the spread is wider.

What this means in practice: if your loading plan depends on a few hundred kilos or a few centimetres, do not work from a table — read the markings on the container allocated to you. Maximum gross, tare and payload are written on the box itself, and for that container those are the binding figures.

Safety approval and inspection status are tracked on the CSC plate. Under the 1983 amendment to the 1972 Convention for Safe Containers the re-examination interval was extended to 30 months, with a choice between the periodic examination scheme and an approved continuous examination programme (ACEP).

Floor and concentrated loads

Staying under the payload does not mean the floor will take the load. Two further limits apply, and for heavy machinery, marble blocks or steel coils they are the real constraint.

Forklift axle load
The floor will carry a forklift with a maximum axle load of 5,460 kg, provided the contact area per wheel is at least 142 cm² (ISO 1496/I). On steel-floor containers this rises to 9,200 kg — enough for any commonly available forklift.
Spread load limit
Where the load is not evenly distributed, the weight per running metre is capped: 4.8 tonnes per metre in a 20' (7.6 tonnes with a steel floor) and 3 tonnes per metre in a 40' (6.0 tonnes with a steel floor). The load may never exceed the maximum payload in any case.

A worked example: place an 8-tonne machine occupying a 2-metre footprint in a 40' and you are at 4 tonnes per metre — far below the payload, but above the 3 t/m limit of a wooden floor. The answers are a spreader frame, a steel-floor container, or a flatrack.

The volume a reefer costs you

The refrigeration unit sits inside the box and takes up space. Most guidance covers temperature ranges and skips this, yet it directly affects the loading plan.

Dry versus reefer capacity — values published by the same carrier
Measure40' HC dry40' HC reeferDifference
Internal length12,032 mm11,578 mm454 mm shorter
Internal height2,700 mm2,525 mm175 mm lower
Capacity76.3 m³66.7 m³12.6% loss
Max payload28,650 kg29,700 kg1,050 kg more

On a 20' the loss is larger still: 28.2 m³ instead of 33.2 m³, a 15.1% reduction. Against that, a reefer's higher maximum gross means its payload exceeds that of the dry box — you lose volume and gain tonnage.

The loss does not end there: a reefer also has a maximum stowage height — space must be left above the cargo for cold air to circulate, and the limit is marked inside the box as a load line. In the published figures the internal height is 2,525 mm while the maximum stowage height is 2,425 mm; the top 100 mm cannot be used. Stowing above that line disrupts the cooling and makes liability for cargo damage arguable.

When it goes wrong

The plan follows an online table and the box does not match

The loading plan is built on 12,032 mm of internal length; the container arrives at 12,029 mm, or from a series whose payload is two tonnes lower. The last pallet will not fit, or the tonnage is exceeded.

Do this: where the plan depends on a few centimetres or a few hundred kilos, get the allocated container number and confirm against its markings.

Heavy cargo loaded into a 40', half the capacity travels empty

With dense cargo — marble, ceramics, canned goods, liquids — a 40' hits its weight limit at half its capacity. Buyers assume "a bigger box carries more", yet a 40' HC's payload is lower than a 20's.

Do this: calculate the density. Above 900 kg/m³, two 20-footers almost always carry more.

Under the payload, but the floor gives way

Heavy machinery on a narrow footprint exceeds the per-metre limit even when the total weight is under the cap. In a 40' with a wooden floor that limit is 3 tonnes per metre.

Do this: measure the contact area, work out the load per metre, and if it exceeds the limit discuss a spreader frame, a steel-floor container or a flatrack.

A reefer is planned like a dry box

A 40' HC reefer is 454 mm shorter and 175 mm lower than its dry equivalent, and nothing may be stowed above the load line. A plan drawn for a dry box leaves the last row outside.

The box is full but the truck is over the legal limit

The container's technical payload is confused with what may legally be hauled by road. Confirm the combination's tare and the applicable weight limit with your haulier before loading.

Frequently asked

How many cubic metres and tonnes in a 20' container?

In the Hapag-Lloyd wooden-floor standard series we used as our source: 33.2 m³ with a maximum payload of 30,200 kg. But the same document also lists a series with a maximum gross of 30,480 kg, where the payload falls to 28,180 kg.

So there is no single right answer. If your plan is tight, read the markings on the container allocated to you.

What is the difference between a 40' DC and a 40' HC?

Height, and nothing else. Internal height is 2,395 mm on a standard 40' and 2,700 mm on a High Cube — about 30 cm more. Length and width are identical.

That lifts capacity from 67.7 m³ to 76.3 m³ but does not raise the payload; because the HC's tare is heavier, its payload is slightly lower. The HC is for light, bulky cargo.

The extra height can also cause bridge, tunnel and gauge problems on inland moves — the carrier's own document carries that warning.

How many pallets fit in a container?

There is no single figure. The answer depends on the pallet size, the stowage pattern, whether double stacking is possible and the weight of the cargo.

The starting point is the internal floor: 5,900 × 2,352 mm in a 20' GP, 12,032 × 2,352 mm in a 40' GP and HC. A 1,200 × 800 mm Euro pallet and a 1,200 × 1,000 mm industrial pallet lay out differently, and double stacking is only possible if the weight and the packaging's stacking strength allow it.

If you would like us to work it out for your shipment, send us the dimensions.

Why does tare matter?

Two reasons. First, payload is maximum gross minus tare — a heavier tare means less cargo. Even between wooden and steel floors of the same type there can be a 50 kg difference.

Second, the verified gross mass (VGM) of a packed container must be declared before it is loaded on a vessel, and one of the permitted methods is to weigh the components and add the tare. A wrong tare means a wrong VGM.

Sources

  1. Hapag-Lloyd — Container Specification Source of every internal dimension, tare, payload, capacity, floor load and concentrated load figure on this page; the carrier's own published equipment specification · hapag-lloyd.com (PDF) · accessed 1 Sep 2026
  2. ISO 668 — Series 1 freight containers (classification, external dimensions) The standard for external dimensions and tolerance limits. The text is a paid publication; only the standard number is cited and nothing is quoted from it. The external dimensions and tolerances appear in the carrier document above with a reference to ISO 668 · iso.org · accessed 1 Sep 2026
  3. IMO — Convention for Safe Containers (CSC 1972) Safety approval plate and inspection regime; the 1983 amendment extended re-examination to 30 months with a choice of periodic examination or ACEP · imo.org · accessed 1 Sep 2026
  4. IMO — Verified Gross Mass (SOLAS Chapter VI, Regulation 2) The VGM declaration and its two permitted calculation methods; MSC.380(94), in force 1 July 2016 · imo.org · accessed 1 Sep 2026

This page is for information only. The dimension and weight figures are taken from Hapag-Lloyd's published document and are valid only for that carrier's stated series; they differ between carriers and between series. Where your loading plan depends on a narrow margin, work from the markings on the container allocated to you. Road weight limits change through administrative measures; confirm with your haulier and the current regulations before shipping.

Change log

  1. Page published. Dimension and weight figures taken from the Hapag-Lloyd Container Specification; density thresholds calculated from the payload and capacity values in that document.