Divide the container's usable volume by one carton's volume, then apply a realistic fill factor of about 85–90%. A 20ft holds roughly 28 CBM of usable space, a 40ft about 58 CBM and a 40ft High Cube about 68 CBM — so a standard 60×40×40 cm carton fits roughly 290 boxes in a 20ft, 600 in a 40ft and 710 in a 40HQ. The exact number depends on your carton size, whether you floor-load or palletize, and whether weight or volume runs out first.
The method in one line
You never fill a container to its raw geometric cube. Between wall clearance, door frames, corner posts, uneven carton stacking and the gaps you can't close, real loads land around 85–90% of the internal volume when floor-loaded by hand. The working formula is:
Cartons per container = (Usable container CBM × fill factor) ÷ CBM per carton
CBM per carton = Length (m) × Width (m) × Height (m)
CBM (cubic meter) is the volume unit used across ocean freight. If you're new to it, start with our full explainer on CBM and container loading, then come back for the carton math.
The catch is that "usable CBM" already bakes in a lot of the loss, so be careful not to double-count the fill factor. In this guide I give you two clean numbers per container — the geometric internal volume and a realistic floor-loaded usable volume — and the table uses the usable figure directly.
Container internal dimensions and volume
These are the widely published 2026 industry-standard figures. Real containers vary by manufacturer and age, so treat them as planning numbers, not contract guarantees — the true tare and payload are stamped on each unit's CSC data plate.
| Container | Internal L×W×H (m) | Geometric volume | Realistic usable CBM | Max payload (kg) |
|---|---|---|---|---|
| 20ft GP | 5.90 × 2.35 × 2.39 | ~33 m³ | ~28 CBM | ~21,700–28,000 |
| 40ft GP | 12.03 × 2.35 × 2.39 | ~67.6 m³ | ~58 CBM | ~26,700 |
| 40ft HQ (High Cube) | 12.03 × 2.35 × 2.69 | ~76.4 m³ | ~68 CBM | ~26,500 |
Dimensions and volumes from CBM Calculator and Seafreightgo; payload figures from Ship4wd against a max gross of 30,480 kg. The 40HQ adds ~30 cm of height over the 40GP — about 8.5 CBM of extra stacking room, which is why it's the default for light, bulky goods.
A worked example
Say you sourced folding storage boxes and your supplier packs them 12 to a carton measuring 60 × 40 × 40 cm.
- CBM per carton = 0.60 × 0.40 × 0.40 = 0.096 m³.
- 40ft GP usable volume = 58 CBM (already discounted for real-world loss).
- Cartons = 58 ÷ 0.096 = 604 cartons → plan for ~600.
- Units = 600 × 12 = 7,200 pieces.
Now sanity-check the weight. If each full carton weighs 18 kg, 600 cartons = 10,800 kg — comfortably under the ~26,700 kg payload, so volume is your limit here and the 600-carton figure stands. Flip the goods to something dense (tiles, hardware, liquids) and you'd hit the weight cap long before the container looks full. Always run both checks.
Approximate carton counts by box size
The table below uses the usable CBM directly (so the fill factor is already applied) and assumes tidy floor-loading. Round down in practice — you can never load the last theoretical box.
| Carton size (cm) | CBM/carton | 20ft (~28 CBM) | 40ft (~58 CBM) | 40HQ (~68 CBM) |
|---|---|---|---|---|
| 40 × 30 × 30 | 0.036 | ~780 | ~1,600 | ~1,890 |
| 50 × 40 × 30 | 0.060 | ~465 | ~965 | ~1,130 |
| 60 × 40 × 40 | 0.096 | ~290 | ~605 | ~710 |
| 50 × 50 × 50 | 0.125 | ~225 | ~465 | ~545 |
| 60 × 50 × 50 | 0.150 | ~185 | ~385 | ~455 |
These are ceilings under ideal stacking. Odd carton shapes, mixed SKUs, "this side up" cartons that can't be turned, and dunnage all pull the real number down. For a single-SKU, cube-friendly carton you'll get close; for a mixed load, shave another 5–10%.
Weight vs. volume: which runs out first
Every container has two ceilings, and your load stops at whichever you hit first.
- Volume-limited ("light and bulky"): pillows, plastics, empty containers, apparel, foam. You fill the cube long before the weight plate matters. The 40HQ is your friend — that extra height is free volume.
- Weight-limited ("dense"): ceramics, stone, machinery, fasteners, canned goods, anything liquid. You hit ~26,700 kg in a 40ft with the floor barely half-stacked, and a 20ft is often the smarter, cheaper choice because you're paying for a box you can't fill anyway.
A quick density rule: divide total shipment weight by total CBM. Above roughly 1,000 kg/CBM you're heavy freight and weight will govern; well below it, volume governs. This is the same trade-off that drives volumetric weight on quotes — worth modelling before you commit to a container size.
Floor-loaded vs. palletized
The counts above assume goods are floor-loaded (hand-stacked directly on the container floor). That's the most volume-efficient method and standard for factory-direct trade-show sourcing.
Palletized loading trades volume for speed and damage protection. A standard pallet (120 × 100 cm or the Euro 120 × 80 cm) eats floor space and its own height, and pallets don't tessellate perfectly against a 2.35 m wide container — you typically lose 10–15% of usable volume versus floor-loading. A 40ft fits about 20–21 pallets on the floor; if cartons can be double-stacked on each pallet, throughput rises but your carton count still falls short of the floor-loaded ceiling.
Rule of thumb: floor-load when labour is cheap at origin and the goods are robust (most China factory loads); palletize when the goods are fragile, the destination warehouse needs forklift handling, or the buyer mandates it.
FAQ
How many cartons fit in a 40ft container?
It depends entirely on carton size. Using ~58 CBM of usable volume: a small 40×30×30 cm carton fits roughly 1,600; a mid 50×40×30 cm carton about 965; a large 60×40×40 cm carton around 600. Divide 58 by your carton's CBM (L×W×H in metres) and round down. Then confirm weight stays under ~26,700 kg.
What is a realistic container fill factor?
For hand floor-loading of a single, cube-friendly carton, plan on 85–90% of the geometric internal volume. Mixed SKUs, non-stackable or "this way up" cartons, and palletizing pull it lower — often 70–80%. The usable-CBM figures in this guide (28/58/68) already apply a floor-loaded factor, so don't discount them a second time.
20ft or 40ft — which should I book?
If your goods are light and bulky, go 40ft or 40HQ: you fill the volume and the per-CBM freight cost drops. If they're dense and you'll hit the weight cap, a 20ft is usually cheaper because the extra volume of a 40ft is wasted. Compute your shipment's density (kg per CBM) first, then decide.
Why can't I load the full geometric volume?
Corner posts, door recesses, wall and roof clearance, the crown of the floor, imperfect stacking and the gaps between cartons all steal space. Cartons are rigid boxes that rarely tile a container perfectly, so 10–15% loss is normal even with careful loading — and more once pallets or mixed sizes are involved.
Does carton size really change the total that much?
Yes. Smaller cartons tessellate better and waste less air, so they yield more units per CBM and resupport cleaner stacks. When you can influence packaging with the supplier, a carton whose dimensions divide evenly into the container's 235 cm width and 239/269 cm height dramatically cuts wasted space — sometimes a 5–10% swing in cartons per container.
Load the whole trip, not just one box
Cartons-per-container is a per-SKU calculation, but a real purchase order is a dozen SKUs each with its own carton size, weight and MOQ. Run any single box through our CBM calculator, size the freight against selling price with the landed-cost calculator, and when you're sourcing on the fair floor, Fairloop captures each product's carton dimensions and quoted price in seconds so your container fill and landed cost are already computed before you leave the stand — see the plan.