How to cut dimensional weight and shipping costs
Carriers charge on the greater of actual weight and dimensional weight. This guide shows how the right box size, a high fill rate and the L×W×H/5000 formula stop you paying for shipped air.
View boxesWhat is dimensional weight and how is it calculated?
Dimensional weight (also volumetric weight) reflects how much space a parcel takes up in the vehicle. Carriers such as DHL, DPD, GLS and UPS bill the greater of actual weight and dimensional weight, so a light but bulky box costs more than the scales suggest.
The formula is length × width × height in centimetres, divided by the volumetric divisor. National parcel services typically use 5000, air freight usually 6000. A 40 × 30 × 30 cm box gives 36,000 cm³ ÷ 5000 = 7.2 kg of dimensional weight, whether it holds 2 kg or 6 kg.
How do you choose the right box size?
Box size is the biggest lever. The box should hold the product plus 2 to 4 cm of cushioning per side, but carry no empty air. An oversized box costs twice: more dimensional weight and more void fill.
- Set the internal size to product dimensions plus about 3 cm of cushioning per side.
- A range of 3 to 5 graduated sizes covers most of your shipments.
- Height-adjustable boxes with tear-off score lines match flat goods.
- Crash-lock base cartons save packing time at the same volume.
- Keep edges just below tariff thresholds (watch girth and length limits).
Graduated sizes and height-adjustable cartons for a high fill rate.
Read the guideHow do you raise fill rate and avoid air?
Every cubic centimetre of air in the box is paid for. The goal is under 10 percent void space while the goods stay safely fixed. This comes from the right box height and slim but effective cushioning, not loose bulk fill.
- Reduce height first: height-adjustable boxes cut the biggest air share.
- Heavy items centred, light items outside keeps the parcel compact and stable.
- Do not lay products diagonally; parallel packing saves edge length.
- Air cushions displace volume without weight and cut breakage risk only, not dim weight - so right-size the box first.
Frequently asked questions
What does the 5000 divisor mean?
It converts parcel volume in cm³ into kilograms: 5000 cm³ equals 1 kg of dimensional weight. National parcel services usually use 5000, air freight often 6000.
Is dimensional weight always charged?
No. The carrier takes the greater of actual weight and dimensional weight. For light, bulky goods the dimensional weight usually wins.
How much cushioning does a box need?
As a rule 2 to 4 cm all round. That protects against damage without creating needless void space, which you also pay for.
Does more void fill lower shipping cost?
No. Void fill lowers breakage risk, not dimensional weight. Only a smaller box with less air actually cuts cost.
Optimise your box range?
We supply graduated folding cartons and height-adjustable boxes so you can control fill rate and dimensional weight.
Right sizes
Graduated boxes for a high fill rate and little air.
Cost aware
Dimensions matched to carrier tariff steps.
Proven quality
Sturdy corrugated protects even with slim cushioning.
Expert advice
We help you pick the right range of sizes.