Container Choice
20ft vs 40ft — which container
should you pick?
Container choice usually comes down to one question: does your cargo hit the weight limit first, or the volume limit? This page turns that judgment call into numbers.
Quick comparison
20ft, 40ft and 40ft HC side by side
| Spec | 20ft Standard | 40ft Standard | 40ft HC |
|---|---|---|---|
| Internal volume | 33.1 CBM | 67.5 CBM | 76.0 CBM |
| Max payload | ~21.7 t | ~26.7 t | ~26.5 t |
| Freight (relative) | Baseline | ~1.5× a 20ft | Similar to 40ft |
| Best for | Heavy, dense cargo | Light, bulky cargo | Bulky, tall cargo |
The rule of thumb: cargo density
A quick kg ÷ CBM check
The most practical yardstick is cargo density (kg/CBM). If your cargo is denser than the container's own "max payload ÷ volume" ratio, weight fills up first and 20ft wins; if it's lighter, space runs out first and 40ft wins.
21,700 ÷ 33.1 ≈ 655 kg/CBM.If your cargo is denser than that (e.g. steel, tile) 20ft is usually more economical; lighter (e.g. apparel, furniture) usually favors 40ft.
Recommendations by situation
Choose 20ft when…
Cargo is heavy and dense, volume is too small to fill a 40ft, or you're routing through roads with strict axle-weight limits.
Choose 40ft when…
Cargo is light and bulky, or volume is high enough that one 40ft beats two 20ft on freight and handling cost.
Choose 40ft HC when…
A 40ft still falls short on height. The extra ~30cm of height adds roughly 13% more volume.
For heavy cargo, think about how it comes off
With dense cargo the choice is not only about freight rates. Load a 20ft close to its roughly 21.7-tonne payload and the box itself is within spec, but you may still run into road weight limits at destination or the rated capacity of the handling equipment.
This matters most for machinery and plant, where a single piece is heavy and has to be lifted by crane or forklift. What fits inside a container and what can be lifted safely are two different numbers, governed by different limits. Splitting the weight across two boxes costs more in freight, but it can take real risk out of the discharge — which is worth pricing in before you book.
Working it through with real cargo
The break-even density differs by box: about 655 kg/CBM for a 20ft (21,700 ÷ 33.1) and about 396 kg/CBM for a 40ft (26,700 ÷ 67.5). If your cargo sits between 396 and 655, a single 40ft fills up on weight first while a 20ft fills up on volume first. That band is where the decision is hardest.
| Cargo | Weight · volume | Density | Decision |
|---|---|---|---|
| Steel parts in cases | 18 t · 12 CBM | 1,500 kg/CBM | One 20ft. 83% by weight, 36% by volume — space left over, but weight governs. |
| Furniture | 7 t · 55 CBM | 127 kg/CBM | One 40ft. 81% by volume. Two 20ft boxes (66.2 CBM) would also work, at higher freight cost. |
| Mixed machinery and materials | 25 t · 40 CBM | 625 kg/CBM | One 40ft (94% weight, 59% volume) or two 20ft. A single 20ft is over on both. |
For cargo in that middle band, don't pick the 40ft on freight rate alone. Road rules cap gross vehicle weight — in Korea at 40 tonnes, with a 10-tonne axle limit. A 40ft tare of about 3.75 t plus 25 t of cargo is 28.75 t for the box alone; add the tractor and chassis (roughly 12–15 t depending on the vehicle) and you can approach or exceed 40 t. Check with the haulier first, or split into two 20ft boxes — often the safer choice once unloading is taken into account.
See exactly how many units fit
Enter your cargo dimensions and the calculator compares piece count and load rate across 20ft, 40ft and 40ft HC automatically.
Open the Loading SimulatorFAQ
Common questions about container choice
Which is cheaper — two 20ft or one 40ft?
One 40ft is usually cheaper than two 20ft on freight and handling. But if your cargo is heavy enough to hit the 40ft's weight limit first, two 20ft may be necessary.
Is the freight gap between 40ft and 40ft HC large?
Usually not. Only the height differs and handling is identical, so the surcharge tends to be small — bulky cargo often gets better value per CBM from the HC.
Density math is a hassle — is there an easier way?
Enter your cargo into the loading calculator and it instantly shows volume and weight load rates for 20ft, 40ft and 40ft HC side by side, so you can see which one fills up first at a glance.