Chargeable weight vs gross weight: what an air waybill is billed on

Air cargo is billed on chargeable weight — the greater of a shipment's actual gross weight and its volumetric (dimensional) weight. Light-but-bulky cargo is billed on the space it occupies; dense cargo is billed on what it weighs. On an air waybill, that one number drives the charge — so a wrong one is a wrong invoice.

Gross weight is what the shipment reads on the scale. Volumetric weight is a weight-equivalent of the space it takes in the aircraft, because a hold fills up by volume long before it hits a weight limit. The carrier bills whichever is larger. A box of pillows and a box of bolts the same size are billed very differently — and the reason is volume, not mass.

How volumetric weight is calculated

The IATA standard is straightforward: volumetric weight in kilograms = length × width × height in centimetres, divided by 6000. The ÷6000 divisor is the IATA standard; some carriers and lanes use ÷5000, which produces a higher volumetric weight. Chargeable weight is then the greater of gross and volumetric, usually rounded up to the next 0.5 kg.

# one shipment, two candidate weights
gross_weight = "85.0 KG"
dimensions   = 120 × 80 × 64 cm
volumetric   = 120 × 80 × 64 ÷ 6000 = 102.4 KG   # 614,400 cm³ ÷ 6000 (IATA)

chargeable   = max(85.0, 102.4) = 102.4 KG   # billed on volume, not mass;
                                             # then rounded up to the next 0.5 kg

Where it goes wrong on a waybill

The chargeable weight is written on the AWB, but it's derived from gross weight and dimensions — so it can be internally inconsistent in ways a plain read won't catch:

• A transposed dimension — 8 × 120 keyed where 80 × 120 was meant — and the volumetric weight is off by an order of magnitude.
• A divisor mismatch — the carrier bills on ÷5000 but the number was computed on ÷6000, or vice versa.
• A chargeable weight below both gross and volumetric — which can't be right, because chargeable is by definition the greater of the two.

Each of those reads as a clean number on the page and lands downstream as a mis-billed charge.

What AWBGuru checks

AWBGuru recomputes volumetric weight from the dimensions on the document and cross-checks the declared chargeable weight against both gross and the recomputed volumetric. When the declared number doesn't line up — a chargeable weight below the greater of the two, or dimensions that imply a very different volumetric — the field is flagged for review rather than trusted. The check follows the IATA ÷6000 standard, with ÷5000 where a carrier or lane uses it.