Container Loading Calculation
A container loading estimate tells you roughly how many cartons or pallets a 20ft or 40ft container can take, based on volume. This guide gives the CBM-based method, a worked example, and a clear warning about why a volume estimate is a planning guide, not a guaranteed fit.
Reviewed by Onno C. P. Boots, publisher of UtilityPilot · Last reviewed: 4 September 2026
Typical internal container volumes
Standard dry containers have widely quoted internal volumes. Real usable volume is always lower than these figures because of packaging, pallet footprints, door frames and stacking limits.
| Container | Assumed internal volume | Planning volume (~80%) |
|---|---|---|
| 20ft standard | ~33 CBM | ~26 CBM |
| 40ft standard | ~67 CBM | ~54 CBM |
| 40ft high cube | ~76 CBM | ~61 CBM |
These volumes are assumptions for planning only. Exact internal dimensions vary by manufacturer and container type — confirm with your carrier.
The CBM-based method
Estimated cartons =
planning volume (CBM) ÷ CBM per carton
Use a planning volume (a realistic percentage of the internal volume) rather than the full figure, because cargo never fills a container perfectly. Apply your own utilisation percentage based on how regular and stackable your cartons are.
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Worked example: 20ft and 40ft
Illustrative figures using an assumed 80% planning utilisation.
| CBM per carton (60 × 40 × 30 cm) | 0.072 |
| 20ft planning volume | ~26 CBM |
| Estimated cartons in a 20ft (26 ÷ 0.072) | ~361 |
| 40ft planning volume | ~54 CBM |
| Estimated cartons in a 40ft (54 ÷ 0.072) | ~750 |
Why a volume estimate is not a guaranteed fit
A volume calculation ignores how boxes actually pack. Non-stackable goods, irregular sizes, pallet overhang, weight limits and door clearances all reduce what really loads. Treat the result as a planning estimate to compare options — never as a promised capacity. Confirm the real load plan with your freight forwarder before booking.
Before you calculate: checklist
- CBM per carton (or carton dimensions to derive it).
- The container type you are considering.
- A realistic utilisation percentage for your cargo.
- Whether cartons are stackable and their maximum stack height.
- Total cargo weight against the container payload limit.
Common mistakes
- Dividing by the full internal volume instead of a realistic planning volume.
- Ignoring weight limits when cargo is dense.
- Assuming non-stackable goods pack as efficiently as stackable ones.
- Treating the estimate as a guaranteed loading capacity.
Assumptions and limitations
Container volumes and the utilisation percentage in this guide are assumptions for planning. Actual capacity depends on packing, weight, stacking and the specific container. UtilityPilot does not guarantee that a given quantity will physically load.
What UtilityPilot can calculate
The container utilisation calculator measures how efficiently your cargo uses container space by volume and weight. Start from the CBM calculator for the volume input, and see the freight tools for the full set.
What you must verify
Confirm exact internal dimensions, payload limits and a realistic load plan with your carrier or freight forwarder. UtilityPilot estimates from the figures you enter and never guarantees loading capacity.
Official sources
UtilityPilot summarises these authorities in its own words. Always verify duty rates and classifications directly with the relevant authority before filing a customs entry.
- U.S. Customs and Border Protection — Entry procedures, valuation, additional duties and rulings guidance. (United States)
- UK Trade Tariff — UK commodity codes, duty rates, VAT and preferential rates. (United Kingdom)
Source registry last updated: 4 September 2026
UtilityPilot helps you organise and estimate import costs. It does not issue binding customs classifications and does not supply live official tariff rates. Verify the final classification and duty rate with the official authority or a licensed customs broker.