Chargeable Weight Calculation and CBM for Air and Sea Freight

Last updated: 10 November 2026

Learn chargeable weight calculation before you ask for a quote, and you will know in advance whether freight will be charged on the actual weight or on the size of your cartons. This article sums up the formulas for air freight, express and sea freight, with worked examples and ways to cut shipping costs.

Quick summary: what is freight charged on?

• Air freight: volumetric weight = width × length × height (cm) ÷ 6,000, and you are charged on the actual weight or the volumetric weight, whichever is higher.
• Door-to-door express: usually divides by 5,000, so the same carton has a higher chargeable weight than with standard air freight.
• Sea freight, less than container load (LCL): volume in cubic meters (CBM) is compared with weight in tons (1,000 kg), and the higher figure is charged.
• Sea freight, full container load (FCL): priced per container, not by weight or volume, but you must stay within the container’s maximum payload.
• The divisor and rounding depend on the provider: always ask for them to be stated clearly in the quotation.

Why is freight not charged on actual weight alone?

Space in an aircraft or a container is limited. Light but bulky goods, such as pillows, lamps or furniture, take up a lot of space but weigh little. Carriers therefore convert carton size into a weight and compare it with the actual weight.

• Actual Weight (Gross Weight): the weight on the scale, including cartons, cushioning material and pallets.
• Volumetric Weight (Volume Weight): a weight calculated from the external dimensions of the packages.
• Chargeable Weight: the higher of the two figures above, which is then multiplied by the freight rate.

Goods that are heavy and compact, such as metal parts, are charged on actual weight. Goods that are light but bulky are charged on volumetric weight.

Chargeable weight calculation for air freight: how does it work?

The IATA air cargo rules (TACT Rules), used by most airlines, state that shipments with more than 6,000 cubic centimeters per 1 kilogram are charged by volume. This gives the following formula:

Volumetric weight (kg) = width × length × height (cm) × number of cartons ÷ 6,000

Put simply, 1 cubic meter of goods by air is charged as about 166.67 kilograms. If your goods weigh less than this per cubic meter, you are charged by volume.

How to measure correctly

• Measure the greatest external width, length and height, including any parts that stick out or bulge.
• If the goods are on a pallet, measure and weigh them including the pallet.
• Under IATA rules, fractions of 0.5 cm or more are rounded up to the next whole centimeter, and fractions below 0.5 cm are rounded down.

Rounding the weight

Under IATA rules for kilograms, a fraction above half a kilogram is rounded up to the next whole kilogram, a fraction below half is rounded up to the next half kilogram, and exactly 0.5 is not rounded. For example, 41.2 kg becomes 41.5 kg and 41.7 kg becomes 42 kg. Some providers may round differently.

Air freight calculation examples (hypothetical figures)

In the first example you pay freight as if the goods weighed 100 kg, even though they weigh only 60 kg on the scale. Air freight also usually has a Minimum Charge: if the calculated amount is below the minimum, the minimum applies.

For service details, see international air freight.

How does the express formula differ from air freight?

Many door-to-door express services usually use a divisor of 5,000 instead of 6,000. For example, DHL Express states the formula width × length × height ÷ 5,000, which is the same as 1 cubic meter = 200 kg. See the DHL Express explanation.

The smaller the divisor, the higher the volumetric weight. Some providers or services may use a different divisor, so check with the provider you will actually use.

Example: same cartons, different divisors (hypothetical figures)

5 cartons of clothing, each 60 × 50 × 40 cm, total actual weight 60 kg.

• Air freight (÷ 6,000): 600,000 ÷ 6,000 = 100 kg
• Express (÷ 5,000): 600,000 ÷ 5,000 = 120 kg

For light but bulky goods, compare prices for both options. For small parcels, documents or samples, express is often more convenient because door-to-door pickup and delivery is included. Read more about our door-to-door air courier service.

How do you calculate CBM for LCL sea freight?

Less than container load shipments are charged on a weight or measurement basis (W/M): volume in cubic meters (CBM, often called “cubes”) is compared with weight in metric tons, and the higher figure is used. The resulting unit is called the Revenue Ton (RT).

1 RT = 1 CBM or 1,000 kg, whichever is higher

How to calculate CBM: width × length × height (cm) × number of cartons ÷ 1,000,000. If you already measure in meters, just multiply the three dimensions and then the number of cartons.

LCL calculation examples (hypothetical figures)

LCL freight is usually priced per RT with a minimum charge. On top of the freight, there are Container Freight Station (CFS) charges at both origin and destination, many of which are also charged per RT. Read more in FCL vs LCL.

How is FCL sea freight charged?

Full container load is priced per container, such as a 20 ft or 40 ft container, whether or not it is full. The more you load, the lower the cost per piece.

What you need to calculate is how many cubic meters of goods fit in the container, and that the total weight stays within the container’s maximum payload and the road weight limits for trucks. See the internal dimensions and payload of each container in the container size guide.

The usable space in a container is usually less than its internal volume, because cartons and pallets do not fit every gap perfectly. Plan the stowage before you book.

Comparing the break-even density of each method

The divisor tells you how much weight 1 cubic meter of goods counts as. If your goods are heavier than this, you are charged on actual weight. If they are lighter, you are charged by volume.

Use this table to see whether your goods count as light or heavy for each method. Choosing the actual method also depends on the unit price, transit time, origin and destination charges, and urgency.

How can you reduce chargeable weight?

1. Choose cartons that fit the goods: empty space in a carton is space you pay for. Cutting a few centimeters off a carton can reduce volume a lot.
2. Disassemble or fold: goods with removable legs or folding parts, such as tables, shelving or steel frames, should be taken apart before packing.
3. Consolidate small cartons into one unit: cartons of the same size stacked on one pallet are easier to measure and charge, and less likely to go missing.
4. Watch the pallet height: pallets stacked unevenly, or with cartons overhanging the edge, are measured from the point that sticks out the most.
5. Choose a pallet size that suits the container or aircraft: common sizes are 120 × 100 cm and 120 × 80 cm. Ask your provider which size loads most efficiently on that route.
6. Use light but strong cushioning material: to reduce actual weight without damaging the goods.
7. Wooden crates and pallets must meet ISPM 15: many countries require wooden packaging to be heat-treated or fumigated and stamped. If it does not comply, it may be held or returned.

If you need help packing or crating goods for shipping, see our packing and wooden crating service.

What information do you need for a quote?

• Number of cartons or pallets, and the external dimensions of each piece (width × length × height).
• Gross weight of each piece, including packaging.
• Product name, and photos of the goods or packages.
• Whether the goods can be stacked, and whether there are fragile or dangerous goods, such as batteries, liquids or chemicals.
• Origin, destination and the date the goods are ready to ship.
• Delivery terms, such as FOB or CIF. See their meaning in Incoterms 2020.

Dimensions and weights should match the Packing List. If the carrier measures or weighs the goods and gets a higher figure than you declared, you will be charged on the measured figure.

Frequently asked questions

Is volumetric weight calculated per carton or for the whole shipment?

For air freight, it is generally calculated for the whole shipment on the same air waybill, comparing the total actual weight with the total volumetric weight. Express services may calculate differently, so ask your provider before shipping.

Why does the invoice show a higher weight than I weighed?

Usually because of volumetric charging, rounding, or measured dimensions larger than declared, for example bulging cartons or cartons overhanging the pallet.

How many kilograms is 1 CBM by air?

With a divisor of 6,000, about 166.67 kg. With a divisor of 5,000, 200 kg.

Can I ship less than 1 CBM by LCL sea freight?

Yes, but providers usually have a minimum charge. For very small shipments, air freight or express may work out cheaper.

Can I measure in inches?

Yes. For air freight, IATA rules use cubic inches ÷ 366 to convert to kilograms, but to avoid confusion, give dimensions in centimeters.