20ft vs 40ft Container: How to Choose for Your Shipment

Choose a 20ft container for heavy, dense cargo and a 40ft (usually a high cube) for light, bulky cargo. A 40' has about twice the volume of a 20' but a similar maximum gross weight, so its payload is no higher and often lower. The deciding number is your cargo's density in kg per cubic metre.

Freight rates change constantly and differ by lane and carrier, so this article gives you the method rather than prices. Plug in your own quotes to decide.

The two boxes side by side

Payloads vary by box: many newer 40' units are rated at 32,500 kg gross, which lifts their payload by around 2,000 kg. Use the CSC plate of the actual container when you are close to the limit. Fuller dimensions are in shipping container dimensions.

Step 1: work out your cargo density

Divide total gross weight by total volume, including pallets and packaging. If you need help with the volume, see CBM calculation.

• Above about 840 kg/m³: even a 20' runs out of weight before space. You cannot fill it; choose a 20' and accept the empty volume. Typical examples are steel, tiles, stone and bagged cement.
• Between about 400 and 840 kg/m³: a 20' can be filled by volume, and a 40' would hit its weight limit with space left. Usually one or more 20' boxes is the efficient choice.
• Below about 400 kg/m³: a 40' fills by volume before weight. Below about 345 kg/m³ the extra height of a high cube is usable too, if the cargo can be stacked.

Step 2: check floor space and height, not just volume

Non-stackable pallets and crates only use the floor, so the comparison is floor positions, not cubic metres. A 20' takes 11 Euro pallets in one tier; a 40' takes 24. If your goods cannot be stacked, cubic capacity is irrelevant and the high cube gains nothing. The pallet arithmetic is in how many pallets fit in a container.

Step 3: compare cost per usable unit

Once you know how much of your cargo each box can actually take, compare the cost per pallet, per cubic metre or per tonne actually shipped:

• Cost per usable m³ = total door-to-door cost of the container ÷ cubic metres you can load in it.
• Cost per tonne = total cost ÷ tonnes you can load (for weight-limited cargo).
• Cost per pallet = total cost ÷ pallets that fit.

Include all costs that change with box size: ocean freight, terminal handling, haulage at both ends, and any overweight or special chassis surcharges. On many lanes a 40' costs noticeably less than two 20' boxes, which is why the 40' usually wins on cost per cubic metre for light cargo. For dense cargo the 40' can carry no more weight than a 20', so you pay for empty space.

Worked examples

The canned food case shows why you need all three checks. The volume is 22 pallets × 1.2 × 0.8 × 1.5 m = 31.7 m³ and the weight 22 × 900 kg = 19,800 kg, which looks like a 20'. But a 20' has only 11 floor positions, and 1.5 m pallets cannot be double-stacked under its 2.28 m door. You need either two 20' boxes (11 each) or one 40' (24 positions, 19,800 kg under the payload). Compare the two quotes; the 40' is often cheaper, and it is one box to handle.

The furniture case checks out the other way: 62 m³ is more than a 40' standard can realistically hold at good utilisation, so the high cube's extra 8.6 m³ is what makes it fit in one box.

Other things that tip the decision

• Road weight limits at origin and destination. A heavy 20' on a chassis can exceed national gross vehicle limits even when the container is within its rating; check before you plan to full payload.
• Equipment availability. Some ports and inland depots have more of one size; a scarce box can mean delays or surcharges.
• Receiver's dock. Some warehouses handle 20' boxes more easily, or have limits on vehicle length.
• Splitting risk. Two 20' boxes can be split across sailings; a single 40' arrives as one.
• 45' high cube boxes add 1.5 m of length and fit 27 Euro pallets, but are not accepted on every lane or road network.

The fastest way to settle a borderline case is to plan it in both boxes. In EveryLoading you can paste the packing list once, switch the vehicle between the 20' and 40' presets in the vehicle tab, and compare what fits, the weight against payload and what is left over.