Container Load Calculator

2. Choose the container. Pick a dry box, a high cube, a reefer, an open top, a double door, a flat rack, or a 48 ft or 53 ft North American box. Or press Choose for me: the planner tries the 20 ft, 40 ft, 40 ft high cube and 45 ft high cube, repeats them as often as the list needs, and keeps the set that carries everything at the lowest freight cost — by the usual ratios between the boxes, or by the rates you enter under Freight — then the least volume.

3. Check the plan and pass it on. The plan appears as you type. Read the checks first, then the steps: for each wall of cargo, what goes in, how it stands, how many across and high, and how much width is left to brace. With one container chosen, a piece can be dragged elsewhere; it turns red where the rules forbid it, and the planner can plan the rest around pieces placed by hand. Then copy a link that opens the same plan on any device, download the positions as a CSV, save a picture of the 3D view, or take the PDF the warehouse loads from.

The volume count is never reached. A 20 ft is 33.2 m³ inside and a 60 × 40 × 40 cm carton is 0.096 m³, so division says 345; the planner loads 270, 78 % of that. Cartons are rigid and the inside is not a multiple of them: across the 2,352 mm width, 5 cartons stand side by side on their 40 cm face and leave 352 mm, which no turn of this carton fills. The loss depends on how the carton’s sides divide the box: small 30 × 20 × 20 cm (11.8 × 7.9 × 7.9 in) cartons fill 91.5 % of a 20 ft, 70 × 50 × 50 cm (27.6 × 19.7 × 19.7 in) cartons 75.4 %.

A few millimetres change the count. The American 24 × 16 × 16 in (61 × 40.6 × 40.6 cm) carton is the counterpart of the 60 × 40 × 40 cm one but slightly larger on every side, and in a 40 ft that costs 30 cartons: 560 against 590. Measure the carton you ship, not the size on the order.

Weight decides before space when cartons are heavy. The counts assume the payload never runs out; divide the payload by the count and you get the average carton mass above which it does: 104 kg (229 lb) for 60 × 40 × 40 cm cartons in a 20 ft, but 45 kg (99 lb) in a 40 ft, which takes more than twice as many cartons on a slightly smaller payload. Above that average, the planner stops at the payload and says so.

The counts use the planner’s defaults: a carton may turn any way, stacks to the roof, and stands with at least 70 % of its base on the cartons below, which is how a strapped or wrapped stack behaves. This side up, a limit on what may stand on a carton, or full support lower them; enter your own carton, rules and quantity to get your count. The table is also an open dataset, free to reuse with attribution: load-cartons.json.

Worked through for that carton. The 20 ft is 5,898 × 2,352 × 2,393 mm inside. Volume first: 33.20 m³ ÷ 0.096 m³ = 345.8, so at most 345 cartons, an upper bound and not an answer. Then the grid, for each way the carton can stand: with its 60 cm side along the length, 9 × 5 × 5 = 225; with it across the width, 14 × 3 × 5 = 210; standing on end, 14 × 5 × 3 = 210. The best single orientation gives 225.

A tighter ceiling. However the cartons are turned, a row of them is some mix of 60 cm and 40 cm sides. Such rows add up to at most 5.8 m within the 5.898 m length, and to at most 2.2 m within the width and 2.2 m within the height, so no arrangement holds more than 5.8 × 2.2 × 2.2 m of carton: 292 cartons. The planner’s 270 is 92 % of that ceiling and 45 more than the best single grid, because it fills the strips the grid leaves empty with cartons turned to fit them.

For one carton size the formula gets close; for a real packing list it does not. Several sizes interlock in more ways than anyone can try by hand, and the count is only the start: heavy pieces must go under light ones, some may not turn or carry anything, the centre of gravity must stay near the middle, every piece must pass the door, and cargo for the first stop must come out first. That is what a load planner adds to the formula, and why a CBM figure says whether a load might fit, not whether it will. For volume alone, the CBM calculator is quicker.

Pallets are counted differently from cartons. A loaded pallet stands upright and is never tipped, so only its footprint turns, and the count is the best floor pattern, with pallets turned where it helps. The pallet calculator draws that pattern for any pallet size; the guides to pallets in a 20 ft container and pallets in a 40 ft container explain it band by band.

A second tier needs two things: the stack must stand under the roof, and each pallet must pass the door. Pallets loaded to 1.1 m (3 ft 7¼ in) stack two high in all four boxes. At 1.5 m (4 ft 11 in) none takes two, not even a high cube: two need 3.0 m against its 2,698 mm inside.

Two tiers also halve what each pallet may weigh. 50 EUR pallets in a 40 ft share a payload of 26,740 kg, 534 kg (1,177 lb) each on average; the figure under each count in the table is that limit. Pallets and cartons can go in one plan: enter both, and the planner stands cartons on pallets only where the pallet line allows something on top.

Centre of gravity along the length. The CTU Code, Annex 7 §3.1.4, asks for the cargo’s centre of gravity to be close to mid-length, with an eccentricity that “should not exceed ±5 % in general” and up to ±10 % “under particular circumstances”, which modern spreaders can compensate. In a 40 ft that is 602 mm either side of the middle, in a 20 ft 295 mm. The planner marks the offset for checking past 5 %, as not allowed past 10 %, and says how far to move the load.

The 60/40 rule is the same rule. The Code gives it as the rule of thumb in the same paragraph: 60 % of the cargo’s mass in 50 % of the length. Across the width, §1.11 asks for the centre to be close to the middle, and the planner applies the same marks; in height it must be below half the height of the cargo space, which the planner measures against the inside of the box, not the top of the stack.

Floor load per metre. A floor carries the full payload spread over its length; for a concentrated load the CTU Code (§3.1.1) defers to the operator. The only per-metre ratings we found are Hapag-Lloyd’s: 4.8 t per running metre (about 3,225 lb per foot) in a wooden-floored 20 ft, 3.0 t (about 2,016 lb per foot) in a 40 ft or 45 ft. So a full 20 ft payload of 28,250 kg needs 5.9 m of floor, nearly all of it. The planner finds the heaviest metre and asks for bearers when it exceeds the rating.

Gross mass and road. Since 1 July 2016, SOLAS chapter VI, regulation 2 makes a verified gross mass a condition for loading a packed container onto a ship. The planner adds the tare to the cargo and compares the sum with the plate; that is the arithmetic of Method 2, but not a VGM, which only a weighing or a certified Method 2 calculation gives. For US roads it uses the cargo carriers usually accept on a standard chassis, about 38,000 lb in a 20 ft and 44,000 lb in a 40 ft, under the 80,000 lb federal limit (23 CFR 658.17); for the EU, the 44 t combined-transport limit (Directive 96/53/EC) less a typical tractor and chassis. Figures per size are in the container weight guide.

The standard sets only a minimum. ISO 1496-1 (1990 text, §5.7) requires the door of an 8 ft 6 in box to be at least 2,261 mm (7 ft 5 in) high and 2,286 mm (7 ft 6 in) wide; Hapag-Lloyd lists 2,565 mm as the minimum height for a 9 ft 6 in high cube. Real doors are a little larger and vary by builder, so the planner uses each container’s door as the dataset records it; see the container door dimensions guide.

So the planner tests a piece against the door in the orientation it will stand in the plan, because a loaded pallet or crate cannot be tipped in the doorway and righted inside. When no allowed orientation passes, the piece is left out with that reason. Allowing it to turn may help; if it may not turn, the answer is an open top, a flat rack or a smaller unit.

One rule applies to the whole load: the Code’s §3.2.3 says heavier cargo should not be stowed on lighter cargo, which also keeps the centre of gravity low. The planner never rests a piece on one lighter than itself, even when that costs some volume.

If you do not know what your cartons can carry, the usual estimate is McKee’s 1963 formula: box compression strength ≈ 5.87 × edge crush test × √(board thickness × box perimeter), in pounds and inches. It is easy but not very accurate, and the lab figure is measured over minutes at 23 °C and 50 % humidity, while a carton in a container is loaded for weeks in damp air. Packaging practice divides it by about 3 to 5: take the figure from the box certificate, divide by 4, and enter the result as the maximum on top. It is a guide, not a guarantee.

The last setting is how much of a base must rest on something. Full support is the safe choice for loose cartons. Wrapped units (70 %) lets up to 30 % of the base overhang a gap, which a shrink-wrapped or strapped unit tolerates because it holds together; it usually loads more.

Stops cost space, because a piece for a later stop may not fill a gap nearer the door than cargo that comes off before it. If the plan with stops leaves pieces out and the plan without them does not, the difference is the price of the route.

When the list is larger than one container, the planner fills containers in turn: the one you chose, repeated, or with Choose for me, every size repeated and runs of high cubes finished by a smaller box, keeping the cheapest set, then the smallest. Each container gets its own tab, checks and steps. A heavy load often needs two 20 ft rather than one 40 ft, because the 40 ft runs out of payload first; figures per size are in the container weight guide.

If something is still left out, the planner tries the changes that most often help — letting a piece turn or carry its own kind, a larger container, partial support — plans each for real, and lists those that load more.

The line varies by carrier and series. In a 20 ft reefer Hapag-Lloyd publishes 2,155 to 2,184 mm, Maersk 2,167 mm and CMA CGM 2,158 mm; in a 40 ft high cube reefer, 2,420 to 2,474 mm, 2,415 mm and 2,394 mm. The planner uses the lowest: 2,155 mm (84.8 in) and 2,394 mm (7 ft 10¼ in). A plan made to those heights holds in any of the three carriers’ boxes.

The gap between inside height and line runs from 83 to 163 mm across these units, so “inside height minus 100 mm” would be wrong both ways. A piece that fits only above the line is left out with that reason. More on the boxes is on the reefer container page.

From Excel. Copy the rows of a packing list from Excel or Google Sheets and paste them into the planner. It reads name, length, width, height, weight and quantity, understands a header row in any language, and names the lines it could not read.

Back to Excel. Download positions gives a CSV file that opens in Excel: every piece, its loading step, its position from the closed end, the left wall and the floor, and its size as stowed. That is the table a warehouse system or a forwarder’s template can take in.

A printable loading plan. Print for the warehouse gives a sheet a crew loads from: the container, seal and VGM written at the top, then one block per wall from the closed end to the door, each with a picture of the container after that wall, what goes in, how it stands, how many across and high, the weight and a box to tick; the checks, lines to sign and a code that opens the plan. The PDF carries the same, plus the 3D view and the side and top views to scale, and the Excel workbook the summary, the steps and every piece’s position. Your company’s name and logo go on both. Loading mode shows the plan on a phone at the container door one wall at a time, asks for a photo at each quarter and at the seal, and gives a loading report. Every file is free, with no email and no watermark; a view-only link lets a client see the plan without changing it.

Loading software. Paid load planning software adds what a free browser tool does not: saved cargo libraries, trucks and air cargo, links to a warehouse or fleet system, and someone to call. For a container or two of cartons, pallets and crates, try the free tools first. We measured four of them, ours included, on the same loads in the container load calculator test.

The plan ignores what it cannot see — dunnage, airbags, lashing, the room a forklift needs for the last pallets, a worn floor — so treat the planned count as the upper limit of what will go in.

The planner builds from the closed end towards the door, placing each block of identical pieces at the lowest, deepest free corner left by the walls and the pieces already loaded (the extreme-point method from packing research), so the load forms walls a crew can follow. It then repeats the construction with seeded variations for a fraction of a second and keeps the best, so the same input gives the same plan. The method is measured on the standard benchmark instances used in packing research, the Bischoff and Ratcliff test problems.

We also typed 10 reference loads by hand into three other free calculators and ours, on 7–8 October 2026. On a 20 ft of 60 × 40 × 40 cm cartons ours loaded 270 in the first container against 262, 258 and 255 in the other three, and on twelve carton sizes it filled 95.4 % of a 40 ft high cube; it was one of two tools to check the door by default and the only one to keep a reefer’s load line. Every result, the method and the raw data are in the container load calculator test, which also says that we built one of the four tools.