Container utilisation: will it fit, and what runs out first

Cartons into a container, and which limit bites first. A load can run out of with a third of the space still empty, and on pallets a third limit arrives: the length budget the columns have to fit inside.

Live result

Weight decides this load, so each container closes at 26,694 kg with 34% of its space empty.

cartons on the sheet1,800
containers needed2 40 foot standard containers
cartons a container1,483

A lighter carton, not a better arrangement, is what fills the space that stays empty.

Loose cartons use one orientation for the whole block, chosen from six orientations. Pallet mode checks two footprint rotations or the complete length frontier for the declared column types. This is a finite enumeration, and the volume bound is not a found layout.

The calculation excludes mixed carton sizes, individual rotations to fill gaps, pinwheel patterns, overhang and mixed products on a pallet. Pallet columns use whole layers and whole pallets, and a plan that exceeds the available length is refused.

Step 1 of 4Which containerClose

Container

FIGURES COMPILED 2026Internal dimensions and tare weights here are the nominal published figures for ISO series 1 dry containers, and the 30,480 kg maximum gross weight is the ISO 668 rating for the 1AA and 1CC types. Individual containers differ by a few centimetres and by a few hundred kilograms, and the plate on the door of the box you are given is the only figure that governs your shipment.

Step 2 of 4How the cargo travelsOn the container floorChange

How it is loaded

Step 3 of 4The carton, and how many

400 \times 300 \times 250

mm · 18.0 kg · 1,800 cartonsChange

Try a scenario

Carton lengthmm

Outside dimensions, as packed. Not the product inside it.

Carton widthmm

Carton heightmm

Weight of one cartonkg

Gross, including the packaging.

How many you are shippingcartons

One carton is

0.030 m³ and 18.0 kg

600 kg a cubic metre, which is dense enough to run out of payload first

Step 4 of 4The limits you are working tono limit high · 900/weekChange

How many may stand on each otherA stack limit is a load bearing limit on the bottom carton, and it is the one people forget until the box is open.

Cartons you use a weekcartons

Cartons the receiving bay takes a daycartons

How it loads

1,483 cartons

A real load is spread and chocked differently and the count is the same.

The block layout	$30 \times 7 \times 9$
Cartons the space allows	1,890
Cartons the payload allows	1,483
Loaded weight	26,694 kg
Space used	65.7%

What this search did and did not find

arrangements evaluated: 6
best arrangement found: 1,890 cartons
: 2,257 cartons
distance from the bound: 367 cartons, 16.3%

The bound is what the volume allows if every cubic millimetre could be used, which no straight block can reach.

Where the limit flips

14.1 kg

What arrives downstream

2 containers

Cartons in the last container	317
Days of demand one container carries	11.5 days
Days for the receiving bay to clear one	4 days
Cartons a container	1,483

1,483 cartons a container is 11.5 days of the demand you set, so one arrives roughly that often and the last one carries 317 rather than a full load. When it does arrive, a bay taking 400 a day needs 4 days to clear it.

Every container type

Same load

20 foot standard

Per container: 882
Containers: 3
Limited by: space

40 foot standard

Per container: 1,483
Containers: 2
Limited by: weight

40 foot high cube

Per container: 1,476
Containers: 2
Limited by: weight

45 foot high cube

Per container: 1,426
Containers: 2
Limited by: weight

Container	Per container	Containers	Limited by
20 foot standard	882	3	space
40 foot standard	1,483	2	weight
40 foot high cube	1,476	2	weight
45 foot high cube	1,426	2	weight

Here is the maths

Model version: 1.0

The formula, in words

Two limits, and you only ever hit one of them. A container has a volume and a payload. Divide the payload by the weight of one carton and you have the most cartons the box may legally carry. Work out how many cartons physically fit and you have the most the space allows. The smaller of those two is your answer, and which one it is changes everything about what to do next.
The block layout. For each of the six ways a rectangular carton can sit, divide the container's length, width and height by the carton's, round each one down, and multiply. The rounding down is where the space goes: a container 12,032 mm long takes 30 cartons of 400 mm and wastes the last 32 mm on every row.
The stack limit is a separate ceiling. Whichever way up the carton sits, no more than the stated number stand on each other, so the height count is the lower of what fits and what the bottom carton can carry.
Density decides the answer before you calculate anything. Divide the container's payload by its volume and you get the density at which the two limits meet: 394 kg a cubic metre for a 40 foot standard, 851 for a 20 foot. A carton denser than that will be weight limited and one lighter than that will be space limited, in that box, always.
This is why dense cargo goes in twenties. A 40 foot container is 2.04 times the volume of a 20 foot and carries 1,550 kg less, because it weighs more empty. Two twenties carry 56,500 kg against a single forty's 26,700, on the same amount of steel.
Length budget: a container is not a count of pallet positions. Take the internal length, take 30 mm off it for the doors, and divide by the length of one pallet column. A 40 foot box gives ten columns of 1,200 mm or twelve of 1,000 mm, and two rows across the width either way. Nothing follows the last column, however much floor is left over.
A mixed container inherits neither type's best case. Columns of 1,200 mm and columns of 1,000 mm satisfy one inequality together: $A \times 1{,}200 + B \times 1{,}000 \le L_u$ , where $A$ is the number of 1,200 mm columns, $B$ the number of 1,000 mm columns, and $L_u$ the usable length in mm. Five long columns are exactly six short ones, which is why every fifth long column costs you two short ones.
The pallet costs you height twice. A deck under each pallet, and 150 mm of clearance under the roof so a forklift can withdraw. Two decks and a clearance is 450 mm of a 2,698 mm container gone before a carton goes in, and layers are whole or they are not layers.
On pallets the weight limit moves. The payload divides by the built column, not by the carton, because the column is what gets loaded and it carries its own decks. A column weight cap can bind long before the plate does: twenty positions at 1,200 kg is 24,000 kg in a container rated to 26,580.

The pallet constants are 30 mm door clearance, 150 mm roof clearance and 25 kg pallet tare. Deck height is the figure entered on the page.

S_l = n_l \times n_w \times n_h

where $S_l$ is the loose space limit, $n_l$ the count along, $n_w$ the count across, and $n_h$ the count high in the highest-count of six orientations.

W_l = \left\lfloor W \div w\right\rfloor

where $W_l$ is the loose payload limit, $W$ the payload, and $w$ the carton weight.

L_u = L - 30\,\text{mm}

where $L$ is the internal length.

H_u = H - 150\,\text{mm}

where $H_u$ is the usable height and $H$ the internal height.

N = \left\lfloor L_u \div L_p\right\rfloor \times r

where $N$ is the positions, $L_p$ the pallet length, and $r$ the rows across.

n_d = n_d^*

where $n_d$ is the cartons on a deck and $n_d^*$ the higher count from the two footprint rotations.

H_c = H_u - H_d

where $H_c$ is the height budget for cartons and $H_d$ the total deck height.

n_h = n_h^*

where $n_h^*$ is the lowest of the roof, stacking and column weight layer limits.

n_c = n_h \times n_d

where $n_c$ is the cartons in a column.

w_c = w_p + w_l

where $w_c$ is the column weight, $w_p$ the empty pallet weight, and $w_l$ the weight of the column’s cartons.

S_p = N \times n_c

where $S_p$ is the pallet space limit.

W_p = N_W \times n_c

where $W_p$ is the pallet payload limit and $N_W$ the whole built columns within payload.

n = n_{\min}

where $n$ is the cartons per container and $n_{\min}$ the smaller applicable limit.

N_c = \left\lceil Q \div n\right\rceil

where $N_c$ is the containers and $Q$ the quantity.

A worked example

Cartons of $400 \times 300 \times 250$ mm, 18 kg each, 1,800 of them, into a 40 foot standard container measuring $12{,}032 \times 2{,}352 \times 2{,}393$ mm inside and rated to carry 26,700 kg.

Lay the carton with its 400 mm side along the container. $\left\lfloor12{,}032 \div 400\right\rfloor = 30$ is 30 rows with 32 mm left over. Across the width, $\left\lfloor2{,}352 \div 300\right\rfloor = 7$ is 7 with 252 mm left. Up the height, $\left\lfloor2{,}393 \div 250\right\rfloor = 9$ is 9 with 143 mm left. That is $30 \times 7 \times 9 = 1{,}890$ cartons, and none of the other five orientations beats it.

Now the payload. $\left\lfloor26{,}700 \div 18\right\rfloor = 1{,}483$ cartons, and that is the smaller of the two, so weight governs. The container closes at 1,483 cartons weighing 26,694 kg and occupying $1{,}483 \times 0.030 = 44.49$ m³ of the 67.72 m³ available. Thirty four per cent of the box is air.

At 1,483 cartons you have filled seven complete tiers of 210 and put 13 on the eighth, in a container that would take nine. 1,800 cartons therefore need two containers, with 317 in the second.

The carton weight at which the two limits meet:

26{,}700 \div 1{,}890 \approx 14.13\,\text{kg}

For the pallet comparison, use cartons of $500 \times 400 \times 300$ mm at 20 kg, 2,100 of them, in 40 foot high cubes. Loose, the 400 by 300 by 500 orientation gives $30 \times 7 \times 5 = 1{,}050$ . Payload allows 1,329, so space decides. The cargo needs exactly two containers at 21,000 kg each.

On $1{,}200 \times 1{,}000$ mm pallets, the usable length is $12{,}032 - 30 = 12{,}002$ mm. Ten columns and two rows give 20 positions. Six cartons tile each deck. The usable height is $2{,}698 - 150 = 2{,}548$ mm; two 150 mm decks leave 2,248 mm, so the roof allows seven 300 mm layers. The 1,200 kg column cap would allow nine.

Seven layers split four on the bottom pallet and three on top. That is 24 and 18 cartons. The pallets weigh 505 kg and 385 kg, so the built column is 890 kg. Twenty columns take 840 cartons and weigh 17,800 kg, including 1,000 kg of pallet. Payload would take 29 columns, or 1,218 cartons, so the floor decides and leaves 148 mm under the roof.

The same 2,100 cartons therefore need two containers loose against three on pallets. The plate never bites here: twenty positions at the 1,200 kg cap is 24,000 kg in a container rated to carry 26,580.

Check it yourself

Switch the container to a 20 foot. The loose block drops to $14 \times 7 \times 9 = 882$ and the payload allows 1,569, so space governs and you need three containers instead of two.

Set the column cap to 700 kg and watch the build drop from seven layers to five, the container from 840 cartons to 600, and 748 mm of height you are still paying for go unused.

What this does not model

Optimal three dimensional packing, mixed carton sizes, turning individual cartons to fill gaps, and pinwheel pallet patterns, all of which a good loader does and none of which is here. Dunnage, airbags, chocking and the space they take. Weight distribution along the container, which matters for the road leg and can make a legal load an illegal axle weight. Road weight limits, which in many countries bind well below the container's own rating. Stacking strength as a real load bearing calculation rather than a number you typed. Temperature, hazardous goods segregation, fumigation and anything that changes what may travel together.

Pinwheel patterns and individually turned pallets to fill gaps, overhang of any kind, mixed products on one pallet, uneven builds where the top pallet is finished with a part layer, slip sheets, pallet collars, the load bearing strength of a deck, and the order columns are loaded in.

The search is a stated enumeration of the six loose orientations, the two pallet rotations or the length frontier. It does not randomise, turn individual cartons, pinwheel a corner or claim that the volume bound can be reached.

The whole record prints. Your browser can save it as a PDF instead of printing it.

A planning estimate, not a load plan, and deliberately not a packing optimiser: it computes one straight block of identical cartons in one orientation, and a skilled loader will usually beat it. Container dimensions and weights are the nominal published figures for ISO series 1 dry containers and every real container differs, so the plate on the door governs and not this page. Road weight limits, axle loads, weight distribution and any restriction on what may travel together are outside it entirely, and in many places the road limit is the one that stops you first.

Load specification

CONTAINER

container: 40 foot standardinternal $12{,}032 \times 2{,}352 \times 2{,}393$ mmdoor $2{,}343 \times 2{,}280$ mm · payload 26,700 kg

CARGO

cargo: carton $400 \times 300 \times 250$ mm at 18.0 kg1,800 cartons to shiploaded on the container floor

THE LIMITS

space: allows 1,890 cartons · binds no
payload: allows 1,483 cartons · binds YES
stack limit: allows not set · binds no
column weight: allows not set · binds no
door: clears · binds no
roof: clears · binds no

THE PLAN

plan: 1,483 cartons a container, 2 containers317 cartons in the last container26,694 kg loaded, 44.49 m³ of 67.72, 34% air

WHAT THE SEARCH DID

arrangements evaluated: 6, a complete enumeration
best arrangement found: 1,890 cartons
volume bound: 2,257 cartons
distance from the bound: 367 cartons, 16.3%