How many pallets fit in a 40 ft container?

Formula, assumptions, and limits

A 40 ft container at the ISO 668:2020 minimum inside size, 11,998 mm long and 2,330 mm wide, takes 24 Euro pallets on the floor, each allowed the 3 mm over size that ISO 6780:2003 permits. Two straight rows take only 23; the 24th needs rows that interlock. The calculator searches the floor layouts, takes the tiers the inside height allows, and caps the result at the payload.

Formula

• $n$: pallets in one floor layout, the maximum taken over every layout that keeps each pallet, at $(a + t) \times (b + t)$, inside $L \times W$.
• $N_{\text{tier}}$: tiers, for loads that can be stacked; 1 otherwise.
• $L$, $W$, $H$: inside length, width and height of the container, mm.
• $a$, $b$: pallet length and width, mm, with $a \ge b$.
• $t$: the pallet tolerance, 3 mm, or 0 for the count at nominal size.
• $h$: height of one loaded pallet, cargo included, mm.
• $P$: payload, the maximum gross mass less the tare, kg.
• $m$: mass of one loaded pallet, pallet included, kg.

Derivation

The floor count is a packing problem: identical rectangles placed in a larger rectangle, each turned either way. The calculator tries three families of layout and keeps the largest count, preferring the simplest on a tie. The first is straight rows along the box, some of turned pallets and the rest lengthwise. The second is every layout made by straight cuts across the box or along it. The third is two interlocking rows: each row starts with pallets one way and finishes with pallets the other way, so the turned pallets of one row sit beside the lengthwise pallets of the other. That family finds the 24th Euro pallet in a 40 ft box at the ISO 668 minimum, and the 21st pallet of 1,200 × 1,000 mm.

Tiers follow from the height alone, and the payload formula is the CTU Code’s: Annex 4, paragraph 2.4, gives the maximum payload as the maximum gross mass less the tare, the attached equipment and the securing material.

Assumptions

• Pallets stand on the floor in their plan dimensions, either way round, with no pallet overhanging another.
• The inside dimensions are clear to the walls. ISO 668 defines them as the largest clear box that fits inside, corrugations excluded.
• Stacked tiers repeat the floor layout exactly.
• The loaded pallet is no wider or longer than the pallet itself.
• The payload covers the cargo and the pallets; dunnage and lashing come out of it before the calculator is used.

Worked example

1. Container: 40 ft standard, 11,998 × 2,330 × 2,350 mm inside, door 2,286 × 2,261 mm, the minimums in ISO 668:2020 Table 3.
2. Euro pallet at its ISO 6780 upper tolerance: 1,203 × 803 mm.
3. Straight rows: 15 × 803 = 12,045 mm and 10 × 1,203 = 12,030 mm are both too long, so a turned row holds 14 and a lengthwise row 9: 23.
4. Interlocked, first row: 1 pallet turned, then 9 lengthwise: 803 + 9 × 1,203 = 11,630 mm.
5. Second row: 1 pallet lengthwise, then 13 turned: 1,203 + 13 × 803 = 11,642 mm. The turned pallets of each row sit beside the lengthwise pallets of the other, and the two rows take 1,203 + 803 = 2,006 mm of the 2,330 mm width, 324 mm free. Floor: 10 + 14 = 24 pallets.
6. A 40 ft high cube, 2,655 mm inside, with loaded pallets 1,300 mm high and stackable: 2,655 ÷ 1,300 = 2.04, so 2 tiers and 48 pallets.
7. At 600 kg a pallet against a payload of 26,500 kg read from the CSC plate: 26,500 ÷ 600 = 44.2, so the payload caps the load at 44.

Edge cases and limits

The Euro pallet count in a 40 ft box turns on 2 mm: two straight rows need 12,000 mm and the ISO 668 minimum is 11,998. A box at least 12,000 mm long inside takes 25 at exact pallet size, and 12,045 mm are needed once each pallet is allowed its 3 mm over size. Thermal containers are narrower: ISO 668 clause 5.3.3 sets only a 2,200 mm minimum inside width for them, which takes two 1,100 mm square pallets across the width at exact size and one at tolerance: in a 40 ft box, a floor of 20 against 10. A layout with a few millimeters to spare leaves a forklift no room to set the last pallet.

Regulatory basis

ISO 668:2020, with Amendment 1:2022, fixes the outside dimensions of series 1 containers in Table 2, the minimum inside dimensions and door openings of general purpose boxes in Table 3, and a maximum gross mass rating of 36,000 kg for the 20, 40 and 45 ft types; ISO 668 names the ISO 1496 series as the authority for inside dimensions. ISO 6780:2003 sets the six pallet sizes and the +3 mm and −6 mm plan tolerance. The CTU Code, approved by the IMO Maritime Safety Committee at its 93rd session and issued as MSC.1/Circ.1497, is not mandatory; it gives the payload formula and the packing practice. SOLAS regulation VI/2, as amended by MSC.380(94), has required a verified gross mass for every packed container before loading since 1 July 2016.

Common errors

• Using the outside dimensions. A 40 ft container is 12,192 × 2,438 mm outside in ISO 668, which suggests 2 Euro pallets 1,200 mm long side by side; the 2,330 mm inside width takes one 1,200 mm side and one 800 mm side.
• Loading only straight rows. In a box at the ISO 668 minimum they take 23 Euro pallets, one fewer than the interlocked layout.
• Quoting a pallet-wide count for a standard box. 33 Euro pallets in a 45 ft container and 30 in a 40 ft need rows of three 800 mm sides across the width: 2,409 mm inside at the ISO 6780 tolerance, 2,400 mm at exact size, and for the 40 ft count 12,030 mm of length, more than the ISO 668 minimum of 11,998.
• Stacking to the inside height and forgetting the door. Two 1,150 mm loads stacked outside stand 2,300 mm and do not pass a 2,261 mm door.
• Reading the 36,000 kg ISO rating as the box’s limit. The CSC plate governs, and a box plated at 30,480 kg carries 30,480 kg less its tare.

Pallets per container by box and pallet size

Floor counts for one tier at the ISO 668:2020 minimum inside dimensions, with each pallet at its ISO 6780 upper tolerance; at exact nominal size the counts are the same. The standard and high cube versions of each length share a floor.

The 1,067 mm square pallet beats the 1,140 and 1,100 mm squares in a 40 ft box because 11 of them fit along the length, 11,770 mm at tolerance, against 10 of the larger ones.

Inside dimensions and doors by container type

ISO 668:2020 Table 3 sets these as minimums for general purpose containers: the inside height is the nominal outside height less 241 mm, and a maker may build any box larger. ISO 668 defines the inside dimensions as the largest clear rectangular box that fits inside, disregarding the top corner fittings where they protrude inward. A particular box can be measured and entered as Custom, as can a reefer, for which clause 5.3.3 sets only a minimum width of 2,200 mm.

Stacking height and the door opening

Two tiers fit when each loaded pallet is no taller than half the inside height: 1,175 mm in a standard box 2,350 mm high and 1,327 mm in a high cube 2,655 mm high, at the ISO 668 minimums. The door is the second check. Pallets stacked outside and driven in as one unit must pass a door at least 2,261 mm high on a standard box, which rules out two 1,150 mm loads that would fit inside. The EPAL Euro pallet is 144 mm high empty, with a safe working load of 1,500 kg, and EPAL allows the bottom pallet of a stack up to 5,500 kg on a solid, even surface.

Payload and the mass limit

Pallet count and mass part company with dense cargo. A 40 ft high cube taking 48 pallets in two tiers against a payload of 26,500 kg is full by mass from 553 kg a pallet, since 48 × 553 = 26,544 kg; from there the payload sets the count. The CTU Code adds two checks the count does not make. A container floor is built to carry the payload spread evenly, and chapter 6, 6.2.6, gives the forklift axle load it must withstand as 5,460 kg, or 2,730 kg a wheel. Annex 7, 3.1.4, limits the eccentricity of the center of gravity to 5% in general, with the rule of thumb of no more than 60% of the cargo mass in either half of the length.

Where to find each input

The maximum gross mass of a particular box is on its CSC safety approval plate, the figure the CTU Code, Annex 4, paragraph 2.2, says to use; the tare is marked on the door, and the payload is the difference. Inside dimensions of a box larger than the ISO minimum come from a tape measure, taken as ISO 668 defines them: the largest clear box that fits inside, so the width between the inner faces of the corrugations. The loaded height and mass come from the packing list or a weighed sample pallet, and the same figure feeds the verified gross mass under SOLAS regulation VI/2 Method 2. Cargo that travels as loose cartons rather than on pallets is counted by volume instead, in cubic meters, with the CBM calculator.

Securing the gaps

The CTU Code, Annex 7, 2.3.6, asks that the void spaces in any horizontal direction add up to no more than 15 cm. The Euro layout in a 40 ft box at the ISO 668 minimum leaves 324 mm across the width and 356 to 368 mm along the length at the door end, one figure for each row, so it needs dunnage, air bags or blocking. Annex 7, 2.3.7, lets the gaps between pallets stay open only where the cargo is firmly secured to the pallets, by lashing or shrink foil, and the pallets are stowed tightly and cannot tip. The calculator shows the free space under the drawing, taking the row that reaches furthest toward the door.