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Freight is sold by space as well as mass.
A carrier bills whichever is greater: what the shipment weighs, or what it takes up converted into kilograms. The number that does the converting is a contract term, and it differs by mode — which is why the same pallets can be 380 chargeable kilograms by sea and 2,240 by air. Put one carton size in and this works out all four at once.
Nothing you type leaves your browser. No account, no form, no upload — the arithmetic runs in the page, and it is the same arithmetic the product runs.
One carton
Off the packing list.
Outer dimensions, not the product's. A carrier measures the box on the pallet, and the gap between inner and outer is the gap between your figure and the invoice.
How many
The whole shipment.
One carton size only. A mixed shipment is the sum of its parts — run each size and add the volumes, or let the product do it from the packing list.
The divisors
From your contract, cm³ per kg.
These are the usual figures. Yours are whatever your carriage contract says, and a divisor of nought is a data error rather than a term — this refuses it by name instead of printing an infinite weight.
Where the divisor comes from
It is a contract term, not a constant.
6,000 cm³ per kilogram is the IATA convention for air, express operators commonly write 5,000, road groupage often 3,000, and sea LCL is charged per revenue tonne — one cubic metre against one tonne, whichever is greater, which is a divisor of 1,000. Those are the usual figures and the ones this page starts from. Your own contract governs, so each one here is editable.
This matters more than it looks. A carrier who quietly bills at 5,000 where the contract says 6,000 adds a fifth to the chargeable weight of every light shipment, on an invoice that looks entirely ordinary. Nobody notices in one month. Over a year it is a number worth having.
There is a second rule this page deliberately leaves out, because it needs your tariff rather than your packing list: the weight break. Where a tariff charges less per kilogram above a threshold, shipping more can cost less, and the shipper is entitled to be billed as though they had reached it. An audit that misses this reports undercharges on correct invoices.
SIAARU checks every freight invoice against the rate card you agreed — chargeable weight, the weight break, each surcharge, and the currency it was converted at — and names the difference line by line. That is FreightAudit AI.