Cubic Weight Calculator
Australian standard 250 kg/m³ (AusPost, StarTrack, Toll) — billable weight as you type.
Enter a box below and the billable weight appears here — the number your carrier charges you for, after its divisor, its dimension rounding and its weight rounding.
Enter a box below and the billable weight appears here — the number your carrier charges you for, after its divisor, its dimension rounding and its weight rounding.
How Cubic Weight Works in Australia
Australian carriers charge parcels on cubic weight when it exceeds the actual weight. The formula: L × W × H (metres) × 250 = cubic weight in kg. Working in centimetres, that is identical to L × W × H (cm) ÷ 4,000 — this calculator uses the exact same math.
Example: a 60 × 40 × 40 cm carton weighing 8 kg → 0.6 × 0.4 × 0.4 × 250 = 24 kg cubic weight. You are billed for 24 kg, three times the scale weight. That gap is why right-sized packaging matters more in Australia than almost anywhere else — the 250 kg/m³ factor is stricter than the international express standard (200 kg/m³, i.e. ÷5,000).
Shipping internationally instead? Use the volumetric weight calculator (÷5,000 for DHL/UPS/FedEx) or the air freight calculator (IATA ÷6,000).
Cubic Weight Worked Examples by Parcel Type
Cubic weight only costs you money when the box is bigger than the goods deserve. These four real parcel shapes show where the 250 kg/m³ factor bites:
| Parcel | Dimensions | Actual | Cubic weight | Billed on |
|---|---|---|---|---|
| Book / documents | 30 × 22 × 5 cm | 1.2 kg | 0.83 kg | Actual (1.2 kg) |
| Shoes in retail box | 35 × 25 × 14 cm | 1.1 kg | 3.06 kg | Cubic (3.06 kg) |
| Pillow / bedding | 60 × 40 × 35 cm | 1.8 kg | 21 kg | Cubic (21 kg) |
| Tools / hardware | 30 × 20 × 15 cm | 12 kg | 2.25 kg | Actual (12 kg) |
The pillow is the cautionary tale: 1.8 kg on the scale, billed as 21 kg. Dense goods (tools, books, liquids) almost never hit the cubic threshold; anything light and lofty almost always does.
Where the Cubic Weight Threshold Sits
A parcel is billed on cubic weight whenever its density falls below 250 kg per cubic metre — that is, under 250 grams per litre of box volume. Practical rule of thumb: if a 10-litre box (roughly 30 × 20 × 17 cm) holds less than 2.5 kg, you are paying for air. Measure the carton, not the product: carriers dimension the outer packaging including bulges, tape and handles, and most round each dimension up to the next centimetre before calculating.
Two exemptions worth knowing: Australia Post states it generally does not apply cubic charging to parcels under 1 kg actual weight, and cubic charging does not apply at all to prepaid satchels or flat-rate packaging — for those, the price is the price regardless of how much air is inside. Contract and eParcel terms vary, so confirm against your own rate card.
Three Mistakes That Inflate Cubic Weight
- Reusing an oversized carton. Going from a 40 cm to a 50 cm cube adds 15.25 kg of cubic weight at 250 kg/m³ (16.00 → 31.25 kg) — usually more than the goods themselves weigh.
- Void fill instead of a smaller box. Air-filled cushioning is billed at the same 250 kg/m³ as the product. Right-sizing beats padding on cost every time.
- Assuming the international rule applies. International express uses ÷5,000 (200 kg/m³), which is 20% gentler than the Australian domestic 250 kg/m³. The same carton costs more to send across town than the divisor maths might suggest.
Sending the same goods overseas? Compare against the international express calculator (÷5,000) or check every carrier factor on the DIM divisor chart.
Cubic Weight FAQ
How do I calculate cubic weight?+
Multiply length × width × height in metres, then multiply by the cubic conversion factor — 250 kg per cubic metre for most Australian carriers. A 40 × 30 × 30 cm carton: 0.4 × 0.3 × 0.3 × 250 = 9 kg cubic weight. In centimetres this is the same as L × W × H ÷ 4,000.
What cubic factor do Australia Post, StarTrack and Toll use?+
Australia Post (including eParcel contracts) and StarTrack use 250 kg/m³. Toll and most other Australian domestic carriers also use 250 kg/m³, though some services and contracts vary — check your rate card.
Do I get charged actual weight or cubic weight?+
Whichever is greater. If your parcel weighs 10 kg but its cubic weight is 15 kg, you pay for 15 kg. Dense parcels are billed on the scale; bulky parcels on volume.
Is cubic weight the same as volumetric or dimensional weight?+
Yes — cubic weight is the Australian/New Zealand term for volumetric (dimensional) weight. International couriers like DHL/FedEx/UPS express the same idea as a divisor: ÷5,000 cm³/kg internationally, which equals 200 kg/m³.
How can I reduce cubic weight charges?+
Use the smallest box that protects the item, compress soft goods, and avoid oversized packaging — at 250 kg/m³, every extra centimetre of box size costs real money on light items.