Shipping Cost Per Unit Calculator
Shipping cost per unit including dimensional weight — the billing rule that makes light bulky items cost far more than they weigh.
Carriers bill on the greater of actual weight and dimensional weight, which is volume divided by a divisor (typically 5,000 for cm/kg).
How the shipping cost per unit calculator works
Carriers bill on the greater of actual weight and dimensional weight, which is volume divided by a divisor (typically 5,000 for cm/kg). A box of 40 × 30 × 30 cm weighing 4 kg bills at 7.2 kg, not 4.
That gap is why packaging size is a freight decision. Shrinking that box to 35 × 25 × 25 cm drops the dimensional weight to 4.4 kg and the billed weight with it.
Formula: dimensional weight = L × W × H / divisor
Worked examples
| Inputs | Shipping cost per unit | Note |
|---|---|---|
| A 40×30×30 box weighing 4 kg | 4.1083 | bills at 7.2 kg |
| A denser box | 6.7083 | actual weight bills |
| A smaller carton | 2.5781 | dimensional weight falls sharply |
FAQFrequently asked questions
What is dimensional weight?
A billing weight derived from the box volume. Carriers charge on whichever is greater — actual or dimensional — because space on a truck is as scarce as payload.
What divisor do carriers use?
Commonly 5,000 for centimetres and kilograms, sometimes 4,000 for express. A smaller divisor means a higher dimensional weight.
At what density does it stop mattering?
At 200 kg/m³ with a 5,000 divisor. Anything less dense than that bills on volume.
How do I reduce freight cost?
Smaller boxes, less void fill, and packing to the carton rather than around the product. Reducing box size is usually cheaper than negotiating rates.
Does this include fuel surcharges?
No. Surcharges are typically a percentage on top and vary weekly; add them to the rate per kilogram if you want them included.
Where these figures come from
- Corporate Finance Institute — EBITDA — why EBITDA is a non-GAAP measure with no single definition
- US SEC — Non-GAAP Financial Measures, Compliance & Disclosure Interpretations — the disclosure rules that exist precisely because EBITDA is not standardised
- Financial Reporting Council — the UK accounting and audit regulator
Last checked: September 2026. These are standard management-accounting definitions; where a term has no single agreed definition, the page says so.