Big, light parcels are where postage can catch a reseller out. Enter the packed dimensions—not the size of the item before wrapping—and compare the cubic result with the parcel’s actual weight.
The cubic weight is higher for this parcel, so its size may affect the postage assessment.
Measure the parcel at its widest points in metres, multiply length by width by height, then multiply the result by 250. If you measure in centimetres, this calculator converts the figures for you.
Australia Post states that own-packaging parcels can be assessed on actual or cubic weight, whichever is greater. Flat-rate packaging is treated differently because the postage is based on the packaging size.
Measure the parcel after it is packed. Include the box, satchel bulge, protective wrapping and any point that increases the outside dimensions.
No. The service, packaging type, destination, account arrangement and Australia Post’s assessment still matter. Use this as a packing check, then confirm the final price with Australia Post.
Australia Post says cubic charging generally is not applied below 1 kg for non-contract lodgements such as MyPost Business, but it reserves the right to apply it—particularly to large, irregular or cylindrical parcels.
It is Australia Post’s published cubic conversion factor: 250 kilograms per cubic metre.