# CBM to kg: converting volume to chargeable weight

CBM is volume and kilograms are weight, so there is no single conversion: it depends on how dense the goods are. Freight uses agreed ratios instead. <b>1 CBM counts as 1,000 kg for sea LCL, 166.67 kg for air (1:6000) and 200 kg for express (1:5000)</b>; you are charged on whichever is greater, the real weight or the volume weight.

## Key takeaways

- Real weight per CBM = density; it varies from under 100 kg (foam) to over 2,000 kg (steel parts).
- Freight ratios turn CBM into a chargeable weight: sea 1:1000, air 1:6000, express 1:5000.
- Compare real and volume weight; the larger is billed.
- Your carrier's agreement sets the ratio; these are common values.

## Why there is no single answer

One cubic metre of feathers and one cubic metre of steel are the same CBM but weigh very different amounts. To turn CBM into real kilograms you need the density of your goods. Freight pricing gets round this by agreeing a **volume-to-weight ratio** for each mode.


## Common ratios

| Mode | Ratio | 1 CBM counts as | 3 CBM counts as |
|---|---|---|---|
| Sea freight LCL | 1 m³ = 1 t (weight or measure) | 1,000 kg | 3,000 kg |
| Road groupage (often) | 1 m³ = 333 kg (1:3000) | 333 kg | 999 kg |
| Express courier | 1:5000 cm³ per kg | 200 kg | 600 kg |
| Air freight | 1:6000 cm³ per kg (IATA) | 166.67 kg | 500 kg |


Road ratios differ most between countries and carriers; 1:3000 is common in European groupage, but check your rate card.


## Worked example

A shipment of 3 m³ weighs 420 kg.

- **By air**: volume weight 500 kg is more than 420 kg, so you pay for 500 kg.
- **By express**: volume weight 600 kg, so you pay for 600 kg.
- **By sea LCL**: 3 m³ against 0.42 t, so you pay for 3 revenue tons.

[Run it in the CBM calculator](https://cartonmath.com/cbm-calculator/?l=100&w=100&h=100&qty=3&wt=140): 3 m³ at 420 kg, with air and LCL chargeable figures.


## Going the other way: kg to CBM

To find how much space a known weight takes, divide by the density. Goods at 250 kg per m³ weighing 1,000 kg take 4 m³. For freight thresholds: 1,000 kg is 1 revenue ton by sea whatever the volume, and 1,000 kg by air equals the volume weight of 6 m³ at 1:6000.


## Find the density of your goods

Weigh and measure one packed carton: density = gross weight (kg) ÷ CBM per carton. A 40 × 30 × 20 cm carton (0.024 m³) weighing 12 kg is 500 kg per m³: heavy for air, average for sea. The US LTL market uses the same idea in pounds per cubic foot; see the [freight class calculator](https://cartonmath.com/freight-class-calculator/).

## FAQ

**How many kg is 1 CBM?**
It depends on what is in it. For freight charges 1 CBM is treated as 1,000 kg by sea LCL, 166.67 kg by air at 1:6000 and 200 kg by express at 1:5000.

**How many kg is 3 CBM?**
3,000 kg for sea LCL charging, 500 kg for air at 1:6000 and 600 kg for express at 1:5000. The real weight depends on the goods.

**How do I convert kg to CBM?**
Divide the weight by the density of the goods in kg per m³. For freight, 1,000 kg is 1 revenue ton by sea, and by air 166.67 kg corresponds to 1 m³ at 1:6000.

**What is a revenue ton?**
The unit for LCL charges: the greater of the volume in m³ and the weight in metric tons.

Source page: https://cartonmath.com/guides/cbm-to-kg/
Updated: 2026-10-06
Publisher: CartonMath (https://cartonmath.com)