A 20GP holds 33.2 m³ and about 28,250 kg, a 40GP holds 67.7 m³ but only about 26,730 kg, and a 40HC holds 76.4 m³ with a payload of about 26,540 kg. In other words, going to 40ft doubles the space but not the weight capacity. The best choice depends on cargo density, road limits and the rate per cubic metre. This guide gives the full comparison table, the method and a set of practical decision rules.
20GP vs 40GP vs 40HC comparison table
| Parameter | 20GP | 40GP | 40HC |
|---|---|---|---|
| Inside dimensions (L × W × H) | 5,898 × 2,352 × 2,393 mm | 12,032 × 2,352 × 2,393 mm | 12,032 × 2,352 × 2,698 mm |
| Door opening (W × H) | 2,340 × 2,280 mm | 2,340 × 2,280 mm | 2,340 × 2,585 mm |
| Internal volume | 33.2 m³ | 67.7 m³ | 76.4 m³ |
| Realistic volume (85%) | 28.2 m³ | 57.5 m³ | 64.9 m³ |
| Floor area | 13.87 m² | 28.30 m² | 28.30 m² |
| Tare | 2,230 kg | 3,750 kg | 3,940 kg |
| Maximum payload | 28,250 kg | 26,730 kg | 26,540 kg |
| 1200 × 1000 pallets, one layer | 9 | 22 theoretical (20–21 in practice) | 22 theoretical (20–21 in practice) |
| EUR pallets, one layer | 11 | 25 theoretical (23–24 in practice) | 25 theoretical (23–24 in practice) |
| Load height per pallet when double-stacked | ~1,150 mm | ~1,150 mm | ~1,300 mm |
| Cartons 600 × 400 × 400 mm | 225 | 500 | 600 |
| Density threshold (payload ÷ internal volume) | ~851 kg/m³ | ~395 kg/m³ | ~347 kg/m³ |
The 85% realistic volume is a rule of thumb for mixed cartons, not a standard. All figures are typical; check the door markings and the CSC plate of the actual unit, or look them up in Container Sizes. Each size is covered in depth in 20ft container dimensions, 40ft container dimensions and 40ft high cube container.
Density decides almost everything
A load "weighs out" when it hits the weight limit before the space is full, and "cubes out" when the opposite happens. The last row of the table marks the tipping point. Cargo at 240 kg/m³ cubes out in all three boxes, so the largest one is usually the cheapest. Cargo at 960 kg/m³ weighs out even in a 20GP.
Ship planners express the same idea as the stowage factor, in m³ per tonne. A density of 400 kg/m³ equals a stowage factor of 2.5 m³/t.
Road limits are often tighter
In Indonesia a container normally travels by trailer between the warehouse and the port. Using the catalogue defaults (20' trailer 24,000 kg, 40' trailer 26,000 kg of container gross mass), the cargo you can safely truck is roughly:
- 20GP: 24,000 − 2,230 = 21,770 kg
- 40GP: 26,000 − 3,750 = 22,250 kg
- 40HC: 26,000 − 3,940 = 22,060 kg
Replace these with the figures in your vehicle's KIR test book and the class of the roads you will use. Run the ODOL Check and read our guide to Indonesian truck sizes.
Cost per cubic metre: the reasoning
Ocean freight is quoted per container, so the cost per m³ falls when a bigger box is genuinely full. The table below uses hypothetical rates purely to illustrate the arithmetic; they are not market rates.
| Option | Example rate | Realistic volume | Cost per m³ | 1200 × 1000 pallets | Cost per pallet |
|---|---|---|---|---|---|
| 1 × 20GP | USD 1,000 | 28.2 m³ | USD 35.4 | 9 | USD 111 |
| 2 × 20GP | USD 2,000 | 56.4 m³ | USD 35.4 | 18 | USD 111 |
| 1 × 40GP | USD 1,600 | 57.5 m³ | USD 27.8 | 20 | USD 80 |
| 1 × 40HC | USD 1,750 | 64.9 m³ | USD 27.0 | 20 (40 double-stacked) | USD 87.5 (43.75) |
The pattern: as long as the cargo is light, the 40GP and 40HC are far cheaper per cubic metre, and the 40HC pulls well ahead when pallets can go two high. For the full picture, add local costs such as the terminal handling charge, trucking and paperwork, which are also charged per box. For small volumes, compare against LCL with the LCL vs FCL Calculator.
Worked example
Shipment A: 50 m³, 12,000 kg (240 kg/m³). It needs 50 / 28.2 = 1.8 20GPs, so two of them (USD 2,000 in our example). A 40GP takes 57.5 m³ realistically, 12,000 kg is far below the road limit, and the example rate is USD 1,600. Choose a 40GP, or a 40HC if the carton heights can use the extra space.
Shipment B: 30 m³, 20,000 kg (667 kg/m³). The volume exceeds the 28.2 m³ realistic capacity of a 20GP. A 40GP has enough space and 20,000 kg is under 22,250 kg. Choose a 40GP; two 20GPs cost more for no benefit.
Shipment C: 25 m³, 24,000 kg (960 kg/m³). The volume fits a 20GP and 24,000 kg is under the 28,250 kg payload, but the 26,230 kg gross mass exceeds a 24,000 kg trailer. A 40GP also exceeds its 22,250 kg road limit. Choose two 20GPs at 12,000 kg each (14,230 kg gross).
Work out your own CBM with the CBM Calculator and our guide on how to calculate CBM.
Factors the numbers do not show
The table and the rates do not tell the whole story. Before you book, also weigh:
- Equipment availability. Some depots hold more 40HCs than 40GPs, or the reverse, and carriers sometimes substitute. Re-check payload and door height if that happens.
- Free time and daily charges. Demurrage and detention run per box per day once free time ends, so two 20GPs mean two bills if you are late. Tariffs and free time are set by the carrier or terminal and vary; check their official rates.
- Unloading at destination. The consignee's warehouse may not have a dock for a 40ft trailer, or may prefer a single box so it unloads only once.
- Split deliveries. Two 20GPs make it easier to deliver to two sites or on two dates, and they spread the risk if customs selects one box for inspection.
- Load security. A full box is easier to pack tight. A large box only half full needs more bracing and lashing to stop the cargo shifting.
Decision rules of thumb
- Below roughly 12–15 m³, compare with LCL first; see LCL vs FCL.
- Density above about 400 kg/m³: start with a 20GP and split across several if needed.
- Density below about 350 kg/m³ and volume above 30 m³: a 40GP or 40HC.
- Stackable pallets with an overall stack height of 2.3–2.6 m: a 40HC.
- Items taller than 2,585 mm: an open top or flat rack.
- Always check the road limit before you lock in the choice.
Common mistakes
- Comparing internal volume instead of realistic volume. Gaps and securing take 10–20%.
- Assuming a 40ft carries double the weight. A 40GP's payload is lower than a 20GP's.
- Forgetting pallet tare. Twenty wooden pallets add about 500 kg.
- Using old rates. Rates move fast; work from a current written quote.
- Ignoring the VGM. A simulation does not replace official weighing; read our VGM and SOLAS guide.
Try it with your own data
Enter your cargo dimensions and weights in Container Compare to see all three sizes side by side, then open the 3D load planner to confirm the layout. The result is a simulation; the final decision still rests on official weighing and the carrier's acceptance.