Who this guide is for
This guide is for owner-managers and fulfilment leads at UK independents and SMEs shipping jewellery, candles and beauty products, boutique fashion accessories, and corporate gifts.
You want:
- Fewer surprise carrier surcharges
- Faster, smoother packing at the bench
- Packaging that still feels premium when it lands on the doormat
Outcome: a UK-focused, carton-pick playbook that helps you stay inside size bands, cut dimensional (DIM) weight, and speed up packing, without adding waste or dulling the unboxing experience.
Related articles you might find useful:
Returns ready packaging that meets courier rules →
Why you’re getting hit with oversize charges
DIM vs actual weight (plain English)
There are two ways carriers look at your parcel:
- Actual weight: What the box physically weighs on the scale.
- Dimensional (or volumetric) weight: A “theoretical” weight based on how much space the parcel takes up:
DIM weight (kg) = (Length × Width × Height) ÷ divisor
(Measurements in cm. The divisor depends on the carrier and service.)
Carriers charge whichever is higher: actual weight or DIM weight.
That’s why big, light boxes are the usual troublemakers. They don’t weigh much, but they hog space in a van. And space, as carriers see it, isn’t free.
Think in size bands (not carrier brands)
Instead of memorising every carrier’s rules, think in size bands. Most UK services follow similar ideas:
- Letterbox-friendly / “PIP Large Letter-style”: Slim, through-the-door formats with tight thickness limits.
- Small-parcel-style: A bit more breathing room, great for candles, small bottles, and boxed sets.
- Medium-parcel-style: Looser limits, but DIM weight can creep up quickly.
Treat published limits as guardrails, not gospel. Always double-check live specs with your carrier, especially ahead of peak.
Want to explore postal box options?
Browse our range of postal boxes →
Carton families that hit the bands
Picking the right box shape (before filling it with hope and void-fill)
- PIP / letterbox-friendly postal boxes (UK): Designed to stay slim. Ideal for jewellery cards, flat accessories, scarves, and lightweight refills.
- Mailer cartons (FEFCO 0427 / 0426 styles): Self-locking, strong edges, quick to build. A solid go-to for Small-parcel-style bands.
- Crash-lock base cartons (FEFCO 0713 / 0711): Fastest to erect (your packers will love them). Just watch the base glue, it can add sneaky millimetres to height.
- Standard RSCs (FEFCO 0201): Cheapest per unit, but rarely the best choice when size bands matter.
Inserts that protect without adding bulk
- Choose card or moulded pulp platforms over foam to save 2–5 mm of thickness.
- Use edge or corner buffers (L-profiles or folded card) instead of loose void-fill that balloons the box.
- For small bottles, diagonal nesting can shave enough length or width to drop a whole size band.
Less air. More intent. Everyone wins.
Build a carton-pick matrix your team can actually use
Map your top 20 SKUs to 1–2 cartons, plus inserts and a fallback. Keep it simple. This should be readable at a glance.
What to include:
- SKU / set name
- Packed product size (L × W × H in mm)
- Target size band
- Primary carton + insert
- Max units per carton
- Fallback carton
- Notes (orientation, padding tweaks)
Example (shortened):
- Ring box: Letterbox-style → PIP box + 2 mm card riser
- Candle (78 mm): Small-parcel-style → Mailer + collar and platform
- Serum bottles: Crash-lock + U-card insert (cross-nest if packing two)
Tip: Keep carton codes short and visible at the pick face, and always show:
- Primary option
- Fallback
- Max units per carton
Your future self (and your packers) will thank you.
Orientation tricks that save space
Sometimes you don’t need a new box, just a new angle.
- Rotate products to reduce the problem dimension (often thickness).
- Stack bottle caps opposing each other to lower overall height.
- Bundle flat items (cards, pouches) with a belly band instead of loose fill.
It’s like Tetris, but with fewer beeps and more postage savings.
Quick DIM wins you can do at the bench
- If thickness breaks the letterbox band: Swap foam → card/pulp and remove unnecessary tissue layers.
- If length is the issue: Rotate the product or insert 90° and dry-fit again.
- If DIM weight is high: Try the next smaller mailer that still protects the edges.
Tape, seals, and sneaky millimetres
- Use H-tape only when needed. Over-taping adds bulk and weight.
- A smaller box + edge protection beats a big box stuffed with fill.
- Final check: panels flush, no bulge, labels inside safe zones.
If it looks stressed, the carrier will be too.
Train once, save daily
Bench card (A6, taped to the table):
- Measure packed product → confirm target band
- Pick Carton A (use fallback if needed)
- Add card/pulp insert to control movement
- Dry fit → check dimensions
- Seal with minimal tape
- Label flat
- Spot-check 1 in 10
First-week audit:
- Log any surcharges and note the cause
- Update matrix notes for repeat offenders
- Share 3 photos of “perfect packs” with the team
Seasonal sanity check:
- Add temporary rows for gift sets and promos
- Test bundles early
- Remove retired SKUs to keep the matrix tidy
A simple DIM calculator you can run in seconds
- Measure packed L × W × H in cm
- Multiply to get volume
- Divide by your service’s divisor (often 4000–6000)
- Compare DIM weight to actual weight. The higher one is billed
Example:
32 × 22 × 12 cm = 8,448 cm³
÷ 5,000 = 1.69 kg DIM
Shave 2 cm off height:
32 × 22 × 10 = 7,040 cm³ → 1.41 kg DIM
Those tiny height reductions? They’re often the biggest money-savers.
Thickness: the make-or-break millimetres
- Mark 25 mm and 35 mm clearly on your bench ruler
- Keep a 25 mm riser block handy for instant pass/fail checks
- If you can see the limit, you’re far more likely to stay inside it.
Ready to explore postal box options?
Browse our range of postal boxes →