CBM to KG — The Two Standards You Need to Know
CBM measures volume; kg measures mass. You cannot directly convert one to the other without knowing the density of the cargo. However, in freight shipping, there are two well-defined billing standards that establish the relationship between CBM and kg for charging purposes.
These are billing conversion ratios, not physical conversions. They define the point at which volume or weight becomes the basis for your freight charge.
| Freight Mode | Standard | Ratio | What it means |
|---|---|---|---|
| Ocean Freight (LCL) | W/M Ton | 1 CBM = 1,000 kg | Pay whichever is higher: total CBM or total kg ÷ 1,000 |
| Air Freight (IATA) | Volumetric Weight | 1 CBM = 6,000 kg vol. | Pay whichever is higher: actual kg or CBM × 6,000 |
Ocean Freight: 1 CBM = 1,000 kg (The W/M Ton)
LCL ocean freight is priced per W/M ton (Weight-Measurement ton). One W/M ton is defined as 1 CBM or 1,000 kg, whichever is greater. Your LCL freight cost = W/M tons × rate per W/M ton.
If CBM > Weight ÷ 1,000: charged on volume (most consumer goods)
If Weight ÷ 1,000 > CBM: charged on weight (dense cargo)
The breakeven density for ocean LCL is exactly 1,000 kg per CBM. Water has a density of 1,000 kg/m³ — so anything lighter than water (which includes almost all packaged consumer goods, furniture, garments, electronics) will be charged on CBM.
Ocean LCL Example
A shipment of 4.5 CBM weighing 2,200 kg, at $50 per W/M ton:
Weight basis: 2,200 ÷ 1,000 = 2.2 W/M tons
Chargeable: 4.5 W/M tons (CBM wins)
Freight cost: 4.5 × $50 = $225
Air Freight: 1 CBM = 167 kg (The ÷6000 Standard)
For air freight, the IATA standard formula is: Volumetric Weight (kg) = CBM × 6,000. The carrier charges whichever is higher — actual weight or volumetric weight. See our full guide on CBM for air freight for worked examples and carrier comparisons.
The "1 CBM = 167 kg" figure comes from the inverse: if 1 CBM equals 6,000 kg volumetric weight, then 1 actual kg produces 1/6,000 CBM of volumetric space = 0.000167 CBM. Or viewed as a density breakeven: cargo with an actual density of exactly 6,000 kg/m³ would have equal actual and volumetric weights — unreachable in practice. More usefully: the breakeven density is approximately 167 kg/CBM (i.e., 1,000 kg/6,000 × something — see our chargeable weight calculator for precise values).
Air Freight Example
0.5 CBM shipment, actual weight 120 kg:
Actual weight: 120 kg
Chargeable: 3,000 kg (volumetric wins)
When Does Volume Matter More Than Weight?
Volume is the chargeable basis when your cargo density falls below the freight mode's breakeven threshold:
| Cargo Type | Typical Density (kg/m³) | Ocean LCL Basis | Air Freight Basis |
|---|---|---|---|
| Garments / Textiles | 100–200 | CBM (volume) | Volumetric (volume) |
| Furniture | 50–150 | CBM (volume) | Volumetric (volume) |
| Electronics / Appliances | 150–350 | CBM (volume) | Volumetric (volume) |
| Plastic goods / Toys | 50–200 | CBM (volume) | Volumetric (volume) |
| Auto parts (steel) | 500–1500 | Often weight | Varies by density |
| Chemicals (liquids) | 800–1200 | Weight or equal | Actual weight |
| Metal / Machinery | 1000–7800 | Weight (mass) | Actual weight |
| Stone / Aggregates | 1500–3000 | Weight (mass) | Actual weight |
CBM to KG Conversion Table
Reference table showing ocean LCL W/M ton comparison and air freight volumetric weight for common CBM values:
| CBM | Ocean W/M equiv. (kg) | Air Vol. Weight (kg) |
|---|---|---|
| 0.1 | 100 | 600 |
| 0.5 | 500 | 3,000 |
| 1.0 | 1,000 | 6,000 |
| 2.0 | 2,000 | 12,000 |
| 3.0 | 3,000 | 18,000 |
| 5.0 | 5,000 | 30,000 |
| 10.0 | 10,000 | 60,000 |
For ocean LCL, the "Ocean W/M equiv." column is the weight equivalent of that CBM. If your actual weight exceeds the W/M equivalent, you pay on weight. For air, if actual weight exceeds the air volumetric weight — which essentially never happens for real cargo — you would pay on actual weight.
Practical Example — Same Cargo, Different Modes
A shipment of plastic storage boxes: 3 CBM, actual weight 180 kg. Rate comparison:
| Mode | Chargeable Basis | Chargeable Qty | Rate | Freight Cost |
|---|---|---|---|---|
| Ocean LCL | CBM wins (3.0 vs 0.18 W/M) | 3.0 W/M tons | $50/W/M | $150 |
| Air Freight | Vol. wt wins (18,000 vs 180 kg) | 18,000 kg | $3.50/kg | $63,000 |
The same 3 CBM shipment costs $150 by ocean LCL and $63,000 by air. This extreme difference is why voluminous, low-density cargo — like plastic storage boxes — is almost never air-freighted. The 420x cost difference makes ocean the only viable option unless urgency demands otherwise.
Enter dimensions and weight. See CBM, W/M tons, and air volumetric weight side by side.
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