Packaging drives delivery cost through four mechanisms: the volumetric or dimensional weight carriers charge on, the size and weight bands that step the price, the surcharges that irregular or oversized packs trigger, and the redelivery and replacement cost of parcels that fail. All four are decided by the pack, not by the product inside it.
Carriers charge for space, not just weight
A vehicle fills up by volume long before it fills up by weight. Carriers price accordingly: most apply a volumetric or dimensional calculation, convert the pack's dimensions into a chargeable weight, and bill the greater of that and the actual weight.
The practical consequence is that empty space inside your box is charged at the same rate as product. A carton that is three centimetres too big in every direction is not a minor inefficiency; it is a line on every invoice.
Bands, not a sliding scale
The second mechanism is that parcel pricing is banded. The cost does not creep up smoothly with size - it holds flat and then steps at a threshold.
That makes near-misses disproportionately expensive. A pack a few millimetres over a depth or dimension threshold moves every order into the next band, and because nothing goes visibly wrong, the mistake can persist for years. postal and parcel packaging covers how to measure against the thresholds.
| Mechanism | What triggers it | What fixes it |
|---|---|---|
| Volumetric weight | Empty space inside the pack | Right-sizing, fitted inserts instead of fill |
| Band step | Dimensions just over a threshold | Measuring packs against published bands |
| Surcharge | Oversize, long, irregular or protruding packs | Knowing the carrier's limits before specifying the format |
| Failure cost | Damage, redelivery, returns | Restraint and protection specified to the real failure mode |
The four ways packaging shows up on a carriage invoice.
Surcharges are a packaging decision
Long, thin, irregular and protruding packs attract handling surcharges because they do not run cleanly through a sorting network. Tubes, poster packs, anything with a handle or a strap, and anything that exceeds a length limit all qualify.
These are avoidable far more often than people assume, because the limits are published. The format can usually be re-specified to sit inside them - see packaging materials for the format options.
The failure cost nobody budgets for
The fourth mechanism is the expensive one. A parcel that arrives damaged costs the product, the outbound carriage, the return carriage, the replacement pack and the replacement carriage - and frequently the customer.
A pack that needs a redelivery because it would not fit through a letterbox costs a second journey. A pack the customer cannot reseal for a return costs you the resale value of the item.
None of that appears under 'packaging' in a management account, which is why packaging looks cheap and delivery looks expensive. See protective packaging and returns management.
How to find out what yours is costing
- Pull a carrier invoice and find the volumetric, oversize and surcharge lines.
- Identify which pack formats generate them.
- Measure those formats - internal and external - against the product that goes in them.
- Measure them against the carrier's published band thresholds.
- Count how many of your orders use each format.
That turns an abstract complaint about carriage into a short list of formats to re-specify. A packaging review does this alongside the material, labour and damage picture.
The fix is usually smaller, not thinner
It is worth separating two different ideas. Making a pack smaller reduces volumetric cost and band exposure. Making a pack thinner or weaker reduces material cost and increases failure cost.
The first is almost always worth doing; the second almost never is on its own. A made-to-size carton with a fitted insert is smaller and stronger at the same time, which is why it tends to win on delivered cost even when it loses on unit price. Parcel despatch and packaging specified together is the version that works best.
The short version
- Carriers charge on volume as well as weight, so empty space is billed.
- Pricing steps at thresholds, so near-misses are disproportionately expensive.
- Long and irregular packs trigger surcharges that are usually avoidable.
- Damage, redelivery and returns are packaging costs charged elsewhere.
- Make packs smaller, not thinner.
Frequently asked questions
What is volumetric weight?
A calculation that converts a parcel's dimensions into a chargeable weight. Carriers bill the greater of volumetric and actual weight, which means empty space in your box is charged as though it were product.
Why did our carriage cost rise when our products did not change?
Common causes are a pack format change, a carrier re-rating its bands, or a surcharge being newly applied to a format you already used. Measuring your packs against the current published bands usually identifies it.
Is it worth changing packaging just to save carriage?
Frequently, yes - because the saving applies to every order rather than once. Model it as delivered cost per order before committing.
Do all carriers charge the same way?
No, which matters if you use more than one. Specify packs that sit inside the tightest of your carriers' limits so the same format works everywhere - see postal and parcel packaging.
Can WSUK look at our carriage and packaging together?
Yes, and they are the same exercise. WSUK runs parcel despatch as well as supplying packaging, so the pack can be specified against the bands you actually ship against.