CBM calculator
Total your cargo in cubic metres across as many carton types as you like — then see the air and sea chargeable weights it implies, and how much of a container it fills.
Cartons
Total volume
1.500CBM
53.0 cu ft · 50 cartons
Total weight
600.0kg
400 kg per CBM
Air chargeable
600.0kg
volumetric 250.5 kg at 167 kg/CBM
Sea revenue ton
1.500RT
greater of tonnes and CBM
Container fill
Dense cargo — 400 kg per CBM. Above roughly 167 kg/CBM, air freight charges on gross weight, and sea freight charges on tonnage rather than volume.
1 CBM = 1,000,000 cm³ = 35.315 cu ft. Air: 167 kg/CBM (IATA ÷6000 basis). Sea: 1 CBM = 1 revenue ton against 1,000 kg. Container capacities are nominal internal volume — plan on about 90% for loose cargo. Source ↗
How to use it
CBM is the number every freight conversation starts with. A forwarder quoting LCL will ask for cubic metres and gross weight before anything else, because between them those two figures decide both the price and whether the shipment should be moving as LCL at all.
- 1
Enter each carton type
One row per carton size, with the number of cartons of that size. Rows can use different units — the calculator normalises everything to metres and kilograms.
- 2
Read your total CBM
You get total volume in cubic metres and cubic feet, plus the air and sea chargeable weights that volume implies.
- 3
Check the container fit
Fill bars show what share of a 20ft, 40ft and 40ft high cube your cargo occupies — against both nominal capacity and a realistic loaded volume.
The CBM formula
Volume in metres, multiplied by quantity, summed across carton types:
CBM per carton = length (m) × width (m) × height (m)
CBM per carton (from cm) = L × W × H ÷ 1,000,000
total CBM = Σ (CBM per carton × quantity)
One cubic metre is 35.3147cubic feet, which is the conversion you need whenever a US-based forwarder quotes in cubic feet while your supplier's packing list is metric.
Measure the outside of the carton, not the contents, and include the pallet if the goods are palletised — overhang and pallet height are space on the vessel and they are charged as such.
Converting CBM to chargeable weight
Volume alone does not price a shipment. Both air and sea compare it against weight and charge on whichever is greater — they simply disagree about the exchange rate between the two:
air: 1 CBM = 167 kg (IATA ÷6000 basis)
sea: 1 CBM = 1,000 kg (one revenue ton)
chargeable = max(actual weight, volumetric weight)
The gap between those two figures is the whole reason mode choice matters. Air treats a cubic metre as worth 167 kg, so anything lighter than that per CBM is billed on volume and air freight gets expensive fast. Sea treats it as 1,000 kg, so the same cargo is comfortably a volume shipment there and the penalty is far smaller.
The 167 kg/CBM line
Work out your density — total kilograms divided by total CBM — and compare it to 167. Below it, you are paying for space on air freight and denser packing pays for itself. Above it, the cargo is weight-driven and shrinking cartons will not lower the bill. The calculator shows this figure with every result.
Container capacity reference
| Container | Nominal capacity | Realistic loaded volume | Typical use |
|---|---|---|---|
| 20ft standard | 33.2 m³ | ≈28–30 CBM in practice | Dense cargo, or a first full container at roughly 15+ CBM |
| 40ft standard | 67.7 m³ | ≈58–60 CBM in practice | The default for volume cargo — twice the space at well under twice the cost |
| 40ft high cube | 76.3 m³ | ≈66–68 CBM in practice | An extra foot of height; usually a small premium over a 40ft standard |
Nominal figures are internal cubic capacity. Loose cartons never reach it — stacking patterns, dunnage and door clearance cost you space — so plan on about 90%. Container specifications are stable; reviewed annually.
Worked example
50 cartons of homeware, China to Rotterdam
Each carton measures 40 × 30 × 25 cm and weighs 12 kg.
40 × 30 × 25 = 30,000 cm³ = 0.03 CBM per carton
0.03 × 50 = 1.5 CBM total
12 kg × 50 = 600 kg total
density = 600 ÷ 1.5 = 400 kg per CBM
At 400 kg/CBM this is dense cargo. On sea freight the revenue-ton comparison is max(0.6 tonnes, 1.5 CBM) = 1.5 revenue tons, so it is still billed on volume — the sea threshold is 1,000 kg/CBM and this is well under it. On air it would be billed on the 600 kg gross weight, since 1.5 CBM implies only 250.5 kg volumetric.
At 1.5 CBM this is firmly LCL territory — about 4.5% of a 20ft container. Consolidating with other orders, or waiting to reach 15 CBM, is where the per-unit freight cost actually falls.
Where CBM estimates go wrong
- Measuring the product, not the carton. The master carton, its filler and its wall thickness are all volume you pay for.
- Forgetting the pallet.Pallet height and overhang routinely add 10–15% to a shipment's CBM and are frequently missing from a supplier's packing list.
- Assuming nominal container capacity. A 20ft container does not take 33 CBM of cartons. It takes about 28.
- Quoting CBM without weight. Forwarders need both; a quote given on volume alone will be revised once the weight arrives.
- Ignoring the LCL surcharges. Per-shipment fees — documentation, deconsolidation, terminal handling — do not scale with CBM, so small LCL shipments carry a much higher effective rate than the per-CBM number suggests.
Accuracy
Estimates only. Carriers and customs authorities determine the final figure — confirm with your carrier before you ship.
How we source and maintain this data
The maths here is definitional: a cubic metre is a cubic metre, and the cm³ to m³ conversion cannot drift. What we do maintain is the surrounding convention — the 167 kg/CBM air factor derived from the IATA 6,000 divisor, the 1,000 kg/CBM sea revenue ton, and the container capacities, all of which are industry standards rather than laws of physics and can move.
The practical load factor is our own guidance rather than a published figure. It reflects what loose cartons actually achieve against nominal capacity, and we label it as guidance on the page rather than presenting it as a specification.
Review cadence: Conversion constants are exact and never change. Container capacities are reviewed annually; chargeable-weight conventions annually and at IATA rate changes. Last reviewed August 2026. This tool is built and maintained by the ParcelTracking team, who run multi-carrier tracking across 3,000+ carriers.
Primary sources
CBM calculator FAQ
CBM stands for cubic metre — the total volume your cargo occupies. It is the basic unit of sea freight pricing and the figure freight forwarders quote LCL rates against. One CBM is a cube one metre on each side, or 1,000,000 cubic centimetres.
Multiply length × width × height in metres for one carton, then multiply by the number of cartons. If you measured in centimetres, multiply the three figures and divide by 1,000,000. A 40 × 30 × 25 cm carton is 30,000 cm³, which is 0.03 CBM.
It depends on the mode. Air freight converts at 1 CBM = 167 kg, which comes from the IATA 6,000 cm³/kg divisor (1,000,000 ÷ 6,000 = 166.67). Sea freight uses 1 CBM = 1,000 kg for the revenue-ton comparison. There is no universal conversion because the two modes make fundamentally different assumptions about how much space a kilogram is worth.
A 20ft standard container has about 33 m³ of internal volume, a 40ft standard about 68 m³, and a 40ft high cube about 76 m³. Those are nominal capacities: loose cartons never stack perfectly, so plan on roughly 90% of the figure — around 28, 58 and 66 m³ respectively.
The greater of your shipment's weight in metric tonnes and its volume in cubic metres. Sea freight is priced per revenue ton — sometimes written W/M for weight or measurement — so a 2 tonne, 5 CBM shipment is charged as 5 revenue tons, and a 10 tonne, 5 CBM shipment as 10.
As a rough rule, LCL — less than container load — makes sense below about 15 CBM, and a full 20ft container starts to win above that. But LCL carries per-shipment handling and deconsolidation charges that scale badly, and it moves more slowly because it waits for co-loaders. Get both quotes at anything over 10 CBM; the crossover point moves with the lane and the season.
Yes, if the goods travel palletised. Measure the loaded pallet including its own height and any overhang, because that is the space the shipment actually occupies on the vessel. A standard pallet adds around 15 cm of height before a single carton is stacked on it.
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