Logistics guides · Freight
Chargeable Weight Explained: How to Calculate CBM and Volumetric Weight
Calculate CBM and chargeable weight for air (1:6000), sea LCL (W/M) and road freight, with worked examples, rate breaks and packing tips to cut costs.
CBM and chargeable weight calculator →
Freight is never charged on weight alone. A carton of pillows and a carton of bolts can weigh very different amounts while taking up the same space in an aircraft, container or truck. To price both fairly, carriers compare actual weight with volume and charge on whichever is greater. This figure is the chargeable weight. Understanding how it is calculated for each mode lets you predict freight costs accurately and design packaging that saves money. Use the CBM and chargeable weight calculator alongside this guide to test your own shipments.
Step one: measure and calculate CBM
Volume in freight is expressed in cubic metres (CBM, m³). Measure each package at its widest points, including pallets, handles and any bulging, in centimetres. Then multiply length × width × height and divide by 1,000,000 to get CBM per package, and multiply by the number of identical packages.
Example: a carton measuring 60 × 40 × 50 cm has a volume of 60 × 40 × 50 ÷ 1,000,000 = 0.12 CBM. Ten such cartons occupy 1.2 CBM. Carriers usually re-measure cargo at their warehouse, so declared dimensions that are too low will be corrected on the invoice.
Air freight: volumetric weight with the 6000 divisor
Under the standard IATA convention, air freight volumetric weight in kilograms is length × width × height in centimetres divided by 6,000. This is equivalent to 1 CBM = 166.67 kg, usually rounded to 167 kg. The chargeable weight is the greater of actual gross weight and volumetric weight, and is normally rounded up to the next half kilogram.
| Shipment | Actual weight | Volumetric weight | Chargeable weight |
|---|---|---|---|
| 10 cartons, 60 × 40 × 50 cm, 18 kg each | 180 kg | 10 × (120,000 ÷ 6,000) = 200 kg | 200 kg (volume) |
| 1 crate, 120 × 80 × 60 cm, 350 kg | 350 kg | 576,000 ÷ 6,000 = 96 kg | 350 kg (weight) |
| 1 pallet, 120 × 100 × 150 cm, 300 kg | 300 kg | 1.8 CBM × 166.67 = 300 kg | 300 kg (equal) |
Express couriers often use a divisor of 5,000 instead (1 CBM = 200 kg), which makes light, bulky parcels more expensive. Under that rule, the 60 × 40 × 50 cm carton above has a volumetric weight of 24 kg rather than 20 kg. Always confirm which divisor a quote is based on.
Air freight rate breaks
Air rates are usually quoted in weight bands, such as minimum charge, under 45 kg, 45 kg and above, 100 kg, 300 kg, 500 kg and 1,000 kg. The rate per kilogram falls as the band increases, so it can be cheaper to be charged at the next break. For example, if the rate is USD 5.00 per kg for 45 to 99 kg and USD 4.20 per kg from 100 kg, a 90 kg shipment costs USD 450 at the lower band but only USD 420 if charged as 100 kg. Airlines and forwarders apply this automatically when the next break is cheaper, but it is worth checking.
Sea LCL: weight or measure (W/M)
For less than container load (LCL) shipments, ocean freight is charged per revenue ton (RT), where one revenue ton is one cubic metre or 1,000 kg, whichever gives the higher figure. This is the weight or measure rule, expressed as a ratio of 1 CBM to 1,000 kg. Most consolidators also apply a minimum, commonly 1 RT, and charge CFS and other local fees on the same basis.
| Shipment | Volume | Weight in tonnes | Chargeable (RT) |
|---|---|---|---|
| Furniture, light and bulky | 3.2 CBM | 1.8 t | 3.2 RT (volume) |
| Steel fittings, heavy and compact | 1.5 CBM | 2.4 t | 2.4 RT (weight) |
| Small sample shipment | 0.4 CBM | 0.15 t | 1 RT (minimum) |
Because 1 CBM equals 1,000 kg in sea freight but only about 167 kg in air freight, light cargo is penalised far more heavily by air. This is one reason bulky, low-value goods almost always move by sea.
Road freight: volumetric ratios vary
There is no single global standard for road freight. Many road carriers and couriers in Asia use 1 CBM = 333 kg, equivalent to a divisor of 3,000 in the formula above, while others use 1 CBM = 250 kg, use loading metres for full and part truckloads, or price by pallet position. Cross-border trucking between Vietnam, China and other ASEAN countries is often quoted per truck or per pallet rather than per kilogram.
Example at 1 CBM = 333 kg: a shipment of 2 CBM weighing 500 kg has a volumetric weight of 2 × 333 = 666 kg, so the chargeable weight is 666 kg. The same shipment by air would be charged at 2 × 167 = 334 kg compared with 500 kg actual, so 500 kg.
Worked example: one packing list, three modes
Consider 20 cartons of 50 × 40 × 40 cm, each weighing 12 kg. Each carton is 0.08 CBM, so the shipment is 1.6 CBM and 240 kg actual. By air, volumetric weight is 1.6 × 166.67 = 267 kg, so the chargeable weight is 267 kg. By road at 1 CBM = 333 kg, it is 1.6 × 333 = 533 kg. By sea LCL, it is 1.6 RT, because 1.6 CBM is greater than 0.24 tonnes. Multiplying each figure by the respective rate shows the true cost difference between the modes.
Summary of conversion factors
| Mode | Typical ratio | Formula (cm) | Chargeable basis |
|---|---|---|---|
| Air cargo (IATA) | 1 CBM = 167 kg | L × W × H ÷ 6,000 | Greater of actual and volumetric kg |
| Express courier | 1 CBM = 200 kg | L × W × H ÷ 5,000 | Greater of actual and volumetric kg |
| Road (common in Asia, varies) | 1 CBM = 333 kg | L × W × H ÷ 3,000 | Greater of actual and volumetric kg, or per pallet or truck |
| Sea LCL | 1 CBM = 1,000 kg | CBM vs tonnes | Greater of CBM and tonnes (revenue ton) |
| Sea FCL | Not applicable | Per container | Flat rate per container within weight limits |
Packing optimisation: paying less for the same cargo
When volume drives the cost, every centimetre of packaging matters. Small changes often reduce chargeable weight by 10 to 30 percent.
- Right-size cartons to the product and remove unnecessary void fill; standardise carton sizes so they stack without gaps.
- Design pallet heights to suit the mode: aircraft contour limits, container height and stacking rules all affect how much fits.
- Avoid marking pallets as non-stackable unless necessary, because carriers may charge for the full height above them.
- Ship items flat-packed, nested or knocked down where possible, especially furniture and fixtures.
- Consolidate many small shipments into fewer, larger ones to benefit from lower rate breaks and avoid minimum charges.
- For dense cargo, check that the floor load and piece weight limits allow you to use the space you are paying for.
- Compare modes: when the chargeable weight by air is far above actual weight, sea-air or rail may offer a better balance of cost and time.
Measure the packed shipment, not the product. Pallets typically add 12 to 15 cm of height, and overhanging cartons are measured at their widest point.
Common mistakes
- Using product dimensions instead of packed dimensions, or forgetting the pallet.
- Calculating air freight with a 6,000 divisor when the courier uses 5,000.
- Forgetting the LCL minimum of 1 RT on very small shipments.
- Rounding dimensions down; carriers round up and re-measure.
- Comparing quotes from different modes or carriers without converting to the same chargeable basis.
GLG’s quotation team calculates chargeable weight for every mode on the same packing list, so you can compare air, sea, road and rail options on a like-for-like basis.
Frequently asked questions
How do I convert CBM to volumetric weight for air freight?
Multiply CBM by 167, or calculate length × width × height in centimetres divided by 6,000. For example, 1.5 CBM is about 250 kg.
What does W/M mean in an LCL quote?
Weight or measure: the freight is charged on cubic metres or tonnes, whichever is greater, with 1 CBM treated as equal to 1,000 kg.
Why does my courier charge more than the airline rule suggests?
Most express couriers use a divisor of 5,000, so each CBM counts as 200 kg instead of about 167 kg.
Is chargeable weight used for FCL shipments?
No. Full container loads are priced per container, as long as the cargo stays within the container’s and the road’s weight limits.
This content is for general guidance and does not replace legal or banking advice for a specific transaction.