When you’re growing an ecommerce business for the first time and finally hit a consistent five hundred orders a month, a proper freight system becomes crucial. Translating freight invoices can often feel confusing though, if you don’t know what they cover. Quite possibly, you estimate a flat shipping fee for a package, only to discover charges far higher than expected in your monthly invoice.
In this article, we’ll help you understand how domestic freight costs are calculated so you can set an accurate budget the next time you’re considering signing a freight service.
Cubic Weight vs. Dead Weight Calculation
Carriers charge based on whichever is greater: the physical scale weight or the volume of truck space you use. A common surprise is seeing a light parcel billed at a 5 kg rate. It can happen since freight networks have limited physical cubic capacity in their vans and linehaul trucks.
To account for light-but-bulky boxes, Australian carriers (such as Australia Post, Aramex, StarTrack) use a standardized calculation called cubic weight, also known as dimensional weight.
The standard cubic conversion factor for Australia Post is 250 kg per cubic metre (factor can vary by carrier and service type. Check with your provider). To find the cubic weight of a parcel, multiply the dimensions in cubic metres, then multiply the result by 250. For example:
A lightweight puffer jacket has a dead weight of 0.8 kg. The box dimensions: 40x30x20 cm (=0.024 m3). Calculation: 0.024 m3 x 250 = 6.0 kg cubic weight.
This means your carrier will charge for 6.0 kg (the higher value).
Conversely, if you ship a liquid beauty serum weighing 3 kg in a box sizing 15x10x10 cm, the cubic weight is only 0.375 kg, but the carrier will bill you for the 3 kg dead weight.
Related: What Is Freight Management? And Why It Matters for eCommerce Business
Shipping Zones, Distance, and Carrier Accessorial Surcharges
Once a package’s billable weight is established, the carrier applies a matrix pricing structure based on geographical zones and operational surcharges.
Freight networks are divided into zones. Shipping a parcel metro-to-metro, from Epping, Melbourne to Sydney Metro, for instance, follows a lower base rate tier. Shipping that same parcel to regional Western Australia or remote Queensland requires interstate linehaul transport and regional courier hand-offs, moving the package into a higher pricing tier.
In addition to the base freight rate, invoices include variable line-item fees known as accessorial charges, which can be categorized as fuel surcharge, residential delivery fee, tailgate fee, and manual handling.
Fuel surcharge is a variable percentage added to the base rate, and it fluctuates monthly based on diesel market prices.
When a carrier needs to deliver to a residential address, not a commercial loading dock, they will charge you a residential delivery fee.
Moving palletized packages on B2B shipments also will cost a tail-lift fee (some called it ‘tailgate’ or ‘liftgate’) if the receiving location lacks a forklift and requires a truck equipped with a hydraulic liftgate.
Last but not least, there are manual handling (or oversize surcharge) fees applied to cartons exceeding standard length (often over 1 metre) or items packed in irregular, non-stackable containers.
Related: The Difference Between Freight and Shipping That eCommerce Businesses Need to Understand
Practical Steps to Audit Freight Invoices
To gain control over freight cost, you don’t have to lower your service standards. By taking a proactive approach to packaging and inventory management, you can keep shipping expenses predictable with these practical ways.
Eliminate excess packaging volume
Review your packaging range. If you usually use a generic carton for small items, select a custom carton size that closely matches your average product dimensions. This switch can reduce your cubic weight charges. The right sizing also helps to dodge manual handling surcharges, since irregular shapes and oversized cartons often can’t move through automated sorting, forcing carriers to charge extra for hands-on processing.
Audit monthly carrier invoices
Freight billing errors do happen sometimes, especially during high-volume sales events. Compare your carrier’s automated billing manifests against your actual order records to check for miscalculated dimensions, duplicate delivery charges, or incorrect address fees.
Utilize aggregated freight networks
Independent ecommerce brands often struggle to access competitive tier rates on their own. Partnering with a 3PL provider allows you to tap into discounted pre-negotiated freight fees while maintaining full visibility into which carrier and service level is used for every shipment.
Mastering freight calculation is just one step in building a cost-effective supply chain. If you’re preparing to scale your ecommerce operations, check out more insights in our blog or download our free 3PL Readiness Checklist to see if you’re ready to scale up.