Tools / Container loading

Container Loading Calculator

Enter the packed size and weight of one unit and the loading plan comes back — units per layer, layers, the volume and payload limits, and which of the two binds first.

Open the calculator Ask us to check it

How many units fit in the container?

20ft or 40HQ · layers, weight limit and utilisation

This calculator answers the question that decides whether an order is economic: how many flat-pack units or panels load into one container. Enter the packed size of one unit, and it returns the loading plan — units per layer, how many layers fit the height, the volume and weight limits, and which of the two binds first.

It does not estimate. If a dimension or the unit weight is missing it returns a list of what is missing instead of a number, because a guessed loading plan is how deposits get lost.

Loading plan

Container Internal length × width × height and payload are the typical published values; confirm with the carrier.

Packed length of one unit (mm) *

Packed width of one unit (mm) *

Packed height of one unit (mm) *

Weight of one unit (kg) * Without the unit weight the payload limit cannot be checked — this is the number most loading plans get wrong.

Stacking limit (layers) If the factory or the packing method allows only a set number of layers, enter it here.

Allow rotating each unit 90°

Reference only: our own flat-pack container houses load 4 units per 20ft and 8 units per 40HQ. Those are our product figures — the calculator above works for any packed size you enter.

Send us the packing list

Send the packed size and unit weight and we will confirm the loading plan against the factory packing method.

Send your drawings

How the calculation works

five steps, no black box

The result is the smaller of two limits — what the volume allows and what the payload allows. Every step is arithmetic you can repeat with a calculator:

Per layer, straight: floor(container length ÷ unit length) × floor(container width ÷ unit width)
Per layer, rotated: the same with length and width swapped. The calculator takes the larger of the two when rotation is allowed.
Layers: floor(container height ÷ unit height), capped if you set a maximum stack.
Volume limit: units per layer × layers.
Weight limit: floor(payload ÷ unit weight). The load is whichever number is smaller.

Container	Internal L × W × H (mm)	Payload
20ft GP	5,898 × 2,352 × 2,393	28,200 kg
40ft HQ	12,032 × 2,352 × 2,698	28,600 kg

These are typical published internal dimensions. Carriers publish their own, and they differ by a few centimetres — always confirm against the carrier's data sheet before booking.

A worked example you can check by hand

1,200 × 800 × 1,000 mm, 45 kg, 40ft HQ

Straight: floor(12032 ÷ 1200) = 10 × floor(2352 ÷ 800) = 2 → 20 per layer
Rotated: floor(12032 ÷ 800) = 15 × floor(2352 ÷ 1200) = 1 → 15 per layer, so straight wins
Layers: floor(2698 ÷ 1000) = 2
Volume limit: 20 × 2 = 40 units
Weight limit: floor(28,600 ÷ 45) = 635 units
Result: 40 units, limited by volume. Volume used 38.4 m³ of 76.4 m³ (50%), payload used 1,800 kg of 28,600 kg (6%)

Notice what the example shows: weight almost never binds for light flat-pack goods, so the packed height is the dimension that changes the answer most. That is why the calculator refuses to guess it.

What this calculator does not do

read this before you quote anyone

It is a volume-and-weight check, not a loading plan. It does not account for:

Pallets, crates or timber bracing — these consume volume and are not in the packed size unless you include them
Mixed SKUs, part loads, or anything that needs load distribution and centre-of-gravity control
Lashing, chocking or dunnage requirements
Irregular shapes, protrusions, or units that cannot be stacked
Road-legal weight limits at destination, which are often lower than the container payload

It is not a shipping document. The final figure has to be confirmed against the actual packing method, the carrier's container data, and the destination's weight rules. We check every loading plan against the factory packing method before a container is booked — that is where deposits get protected.

This tool is also available as a callable MCP server for AI agents at https://buildextechnology.com/api/mcp, so a sourcing assistant can run the same arithmetic and cite it.

FAQ

Is a 20ft or a 40HQ container better for flat-pack units?

A 40HQ carries roughly twice the volume of a 20ft and relatively less weight per unit of volume, so tall light units suit it best. Enter both container types in the calculator with your packed size and compare the units you can load.

Why does the calculator ask for the unit weight?

Because volume and payload bind differently. A container can be volumetrically full and still be under its payload limit, or the other way round. The calculator reports both and tells you which one limits the load.

What if I do not know the packed height yet?

Then the calculator returns what is missing rather than a number. The packed height is normally confirmed with the factory packing method, and it changes the number of layers more than any other dimension.

Do you confirm the loading plan before booking?

Yes. Send the packed size and unit weight with your enquiry and the loading plan is checked against the actual packing method before the container is booked.