Three parcels, one item, three different freight totals
Below are three reconstructions of the same order shipped twice, built from the stage order and from weight arithmetic. No invoice from any operator is reproduced, and every kilogram figure is ours, chosen so the divisions are visible. What the 3 have in common is that the contents barely changed and the freight line moved anyway.
| Case | What changed | Billed weight | Freight effect |
|---|---|---|---|
| One: the carton | One side of the box grew 5 cm while the contents stayed identical | 5.00 kg to 5.63 kg | Up 12.5% at an unchanged per-kg figure |
| Two: the timing | Same box, same contents, shipped 9 days later | 5.00 kg, unchanged | Depends on the rate in force that week; no published figure held here |
| Three: the split | One 5.70 kg parcel became two parcels of 3.10 kg and 2.60 kg | 5.70 kg across two invoices | Two per-parcel lines where there used to be one |
The first and third cases are arithmetic you can reproduce on a kitchen table with a tape measure. The second is not, which is exactly why it is worth separating: 2 of the 3 causes are under your control and 1 is not.
Case one: a carton that grew 5 cm in one dimension
Everything in this case was settled before packing, when a 4.2 kg set of contents was placed in a 40 × 30 × 25 cm carton. That carton measures 30,000 cm³, and air freight bills the greater of actual and volumetric weight, so at a 6,000 divisor it bills 5.0 kg. Adding a puffer jacket pushed one side to 45 cm: 33,750 cm³, 5.63 billed kg, and 0.63 kg charged for a garment that weighs well under 1 kg.
What was actually being decided was not "add the jacket" but whether to put it in the same box or send it in a second, smaller parcel — and the honest answer needs two quotes, because the second parcel carries its own minimum charge. What the arithmetic does settle is the size of the first option: 12.5% more on the freight line, with nothing added to the parcel.
- Measure the carton, not the contents: length × width × height in cm, then divide by the divisor on the carrier card
- Compare the result against the scale weight and pay attention to whichever number is larger
- Ask the warehouse to repack into the smallest carton that closes, before the parcel is sealed
- Remove retail packaging on anything bulky, since 0.3 to 0.5 kg of a billed weight is often cardboard
The [chargeable-weight](/rig/chargeable-weight/) rig runs the division for a carton you measure. It exists because this case is the most common way a 2nd parcel costs more while weighing exactly the same.
The cheapest version of this case costs nothing at all. Measure the carton before it is sealed, ask for a repack into the smallest box that closes, and compare the new dimensions against the old ones: a 5 cm change on 1 side is what moved the billed weight 0.63 kg here, which is more than most people expect 1 extra garment to cost.
The 6,000 divisor used above is our assumption for the arithmetic. No carrier card was available for this note, so read the divisor printed on the card that applies to your parcel.
Case two: the second parcel left nine days later
Nothing about this case is measurable from a desk. The same 5.0 kg box left the warehouse 9 days after the first one, landed inside a period when the lanes were full, and paid a different rate for identical weight. Peak periods are visible in advance — public holiday calendars are published by governments, and the [season-calendar](/rig/season-calendar/) rig plots them against a shipping date you choose.
This one was settled 2 weeks earlier, at the moment the item was ordered rather than the moment the freight was paid. A seller who takes 6 days instead of 2 puts an item into the warehouse on day 8 instead of day 4, and the parcel then sits until you pay — which is the one part of the schedule you control completely.
What cannot be written down here is a number. No surcharge amount, percentage or peak window is quoted on this page, because none could be verified. The transferable part is procedural: ask the operator, in writing, for the rate in force on the date you intend to pay, and compare that against the rate you were quoted 14 days earlier.
Case three: one parcel became two to arrive sooner
A 5.70 kg parcel was split into 3.10 kg and 2.60 kg so that the first part would move immediately. The weight did not change — 3.10 plus 2.60 is still 5.70 kg — but the parcel count did, and per-parcel lines are charged per parcel. Two minimum charges, two handling lines and two deliveries replaced one of each.
A deadline is the only justification that works here, and it has to be a real one. If nothing has to arrive by a date, the split buys speed with money and the arithmetic rarely favours it. If something does have to arrive by, say, day 20, the split is a purchase of time, and the honest comparison is the second invoice against the cost of missing the date.
- Add the two per-parcel lines together before comparing: a minimum charge plus handling on each parcel is often larger than the weight saving
- Check whether the heavier half crosses a weight band that the combined parcel was already in
- Keep both tracking numbers and both invoices; a claim on a split shipment needs the parcel it belongs to
The [consolidation](/table/consolidation/) page covers what merging does to the same arithmetic in reverse, and the split decision is best read next to it, because both are 1 question asked in 2 directions.
What carries over to the parcel you are packing now
- Carton dimensions, not contents weight, decide the billed number on anything bulky — measure before sealing
- One box for four light items beats four boxes, and beats one taller box that crosses a volumetric step
- Timing is the only lever that costs nothing to pull, and it has to be pulled before the seller is paid
- Per-parcel lines are the fixed cost of every additional shipment; count them before a split looks attractive
- Every change is cheaper at the QC stage than after freight is paid, because after payment the parcel is sealed and priced
A single check catches all three cases before money moves: write the carton size, the scale weight and the ship date on one line, then compare that line against the previous parcel. Two numbers that moved and one that did not tells you which of the three causes you are looking at in about 2 minutes.
The [pay-freight](/steps/pay-freight/) step is the last moment any of it can be changed. After that payment the weight is billed, the address is fixed, and 1 question remains: when the box lands.
Where the money went is worth writing down once per parcel, because case three is the one people repeat. Two parcels of 3.10 kg and 2.60 kg carry 2 minimum charges, 2 handling lines and 2 delivery attempts; had the same contents moved as 1 parcel of 5.70 kg, 2 of those lines would not exist.
No carrier rate card, surcharge table or operator invoice was available for this note. Every figure above is either arithmetic on stated assumptions or marked as unpublished.
Worked example: 4.2 kg of contents in a 40 × 30 × 25 cm carton bills 5.0 kg at a 6,000 divisor; growing one side to 45 cm makes the carton 33,750 cm³ and the billed weight 5.63 kg, a 12.5% freight increase with nothing added inside. The divisor is a stated assumption for the arithmetic, not a carrier quote.
This note explains the mechanics; the list is where the items are.