Chargeable Weight Calculator: Air Freight (IATA & Express)

By Owen Hartley, Editor · Last updated November 11, 2026

Enter every piece in the shipment. The calculator works out volume weight, compares it with gross weight and shows the chargeable weight under the IATA air cargo rule and under each express carrier's divisor.

How airlines calculate chargeable weight

Under the IATA rule, measure each piece's greatest length, width and height, round each to the nearest whole centimeter, multiply, add up all pieces and divide by 6,000. That gives volume weight in kilograms. The airline charges the higher of volume weight and gross weight, rounded up to the next half kilogram.

The same rule works in inches: divide cubic inches by 366 for kilograms or by 166 for pounds. In pounds, any fraction rounds up to the next whole pound. These steps come from IATA's TACT Rules 3.9.4 as quoted in an ASEAN and FIATA freight-forwarder training module; the TACT manual itself is a paid publication.

A worked example from that module: one skid of 162.2 × 155.6 × 141.4 cm rounds to 162 × 156 × 141 cm, which is 3,563,352 cubic centimeters. Divided by 6,000 that is 593.892 kg, rounded up to 594.0 kg.

IATA 6000 vs express carrier divisors

Express carriers divide by a smaller number, which makes the same box heavier. FedEx International and DHL Express use 5,000 cubic centimeters per kilogram, so volume weight comes out 20 percent higher than under the IATA 6,000 rule. In inches and pounds, UPS lists 139 for Daily Rates and 166 for Retail Rates.

Source: ASEAN / FIATA training module, Chapter 5: Calculation of Air Freight (quotes IATA TACT Rules 3.9.4 and weight computation rules); FedEx, How do I calculate dimensional weight of a package? (customer support FAQ); DHL, Weight and Dimensions (DHL Express, discover.dhl.com, GB); UPS, Package Dimensions, Size Limits and Weight Guide (US support page), checked Oct 30, 2026

— not stated by source

• IATA (TACT Rules 3.9.4), General air cargo: Dimensions round to the nearest whole unit (0.5 rounds up). Volume weight is kept to 3 decimals, then rounded: kilograms up to the next 0.5 kg (exactly .5 stays), pounds up to the next whole pound. Some lanes use 7,000 cm³/kg; those exceptions are not covered. IATA's TACT rules are a paid publication; the rule is quoted from an ASEAN and FIATA training module.
• FedEx, International (FedEx Express): FedEx rounds each dimension up to the next whole unit but does not state how the resulting weight is rounded; the calculator shows it unrounded.
• DHL Express, International express: DHL's page does not state a rounding rule. DHL Express's 2025 weights and dimensions sheet gives the same factor, 1/5000 m³ (200 kg/m³).
• UPS, Daily Rates (US), UPS, Retail Rates (US): The UPS divisor depends on the rate type. Rounding rules are in the UPS Rate and Service Guide, which we have not checked.

The calculator shows all rows side by side for your pieces, and the difference against the IATA result in kilograms and in percent. Pick one row to make it the headline result. Your own contract may set a different divisor; in that case, use the custom divisor field.

When volume weight beats actual weight

Volume weight wins whenever the shipment is lighter than the divisor's built-in density. The IATA rule equals about 166.7 kg per cubic meter; a 5,000 divisor equals 200 kg per cubic meter. In US units, 166 cubic inches per pound is about 10.4 lb per cubic foot, and 139 is about 12.4.

A carton of 60 × 50 × 40 cm weighing 10 kg shows the effect. Its volume weight is 20.0 kg under the IATA rule and 24.0 kg with a 5,000 divisor, so the bill is based on 20 or 24 kg instead of 10. Smaller cartons and less void fill are the only ways to bring volume weight down.

Rounding rules by carrier

Rounding changes the final number more than people expect. The IATA rule rounds each dimension to the nearest centimeter, keeps three decimals, then rounds weight up to the next half kilogram; exactly .5 stays. FedEx rounds each dimension up to the next whole centimeter or inch. DHL and UPS do not state a rounding rule on the pages we checked.

Where a carrier's published page does not state a rule, the calculator shows the unrounded result and says so under it, rather than guessing. Another difference: IATA adds the volume of all pieces before dividing, while DHL says to work out each piece separately. The calculator follows each source's method.

Unit conversions and test cases

Inputs in inches or centimeters are kept in the units of the chosen rule; when a rule exists only in other units, the calculator converts, computes and converts back, and says that it did. Conversions use 1 inch = 2.54 cm and 1 pound = 0.45359237 kg exactly.

Fourteen test cases run on every build, including every worked example from the IATA training module, a case where gross weight wins, the exact-half-kilogram rule, one example each for FedEx, DHL and UPS, and a contract divisor. If a single result changes, the page is not published until it is fixed.