The Hidden Tax: How Shipping Air Drains Your Margin
Every major carrier (UPS, FedEx, DHL, DPD, GLS) prices parcels by dimensional weight, not just actual weight. Dimensional weight is calculated as length x width x height divided by a DIM factor (typically 5,000 for metric, 139 for imperial). If the dimensional weight exceeds the actual weight, you pay for the air.
Here’s an example. A box measuring 40x30x30 cm with a DIM factor of 5,000 gives you a dimensional weight of 7.2 kg. If the actual product inside weighs 2 kg, you’re paying for 7.2 kg of shipping. That’s 3.6x overpayment on weight-based rates.
Now multiply that across every parcel, every day. The numbers add up fast.
The annual shipping cost range assumes a blended rate of $4.50–$6.30 per parcel across carriers. The $1.1M–$1.6M savings comes primarily from right-sizing boxes (lower DIM weight charges) and secondarily from reduced material costs and fewer pallets.
Why Are Warehouses Still Shipping Air?
Three reasons. All fixable.
Reason 1: Too Few Box Sizes
Most warehouses stock 4-8 box sizes. That seems like enough until you realize that the gap between a "medium" and a "large" box might be 10 liters. If an order fits in 12 liters but your medium is 8 and your large is 18, you're shipping 6 liters of air in every large box.
The fix isn't buying 50 box sizes (that creates its own chaos at the pack station). It's analyzing your order data to find the optimal 8-12 box sizes that minimize total void across your actual order distribution. Cartonization software does this analysis automatically.
Reason 2: Packers Choose by Instinct
A packer at a station grabs the box that looks right. They're fast, experienced, and usually close. But "close" means 10-20% too big on average.↗ That's human judgment doing its best with a time constraint: the packer needs to move, not stand there comparing boxes.
Software removes that decision. The packing station screen shows: "Use Box C (35x25x20). Place item A flat, item B on top, item C standing." The packer follows the instruction. Done. No judgment call, no waste, no variation.
Reason 3: Nobody Measures the Cost
Most warehouses track shipping cost per order as a blended number. They don't break it down into DIM weight overpayment, void fill waste, and corrugated cost per order. If you can't see the waste, you can't fix it.
A quick diagnostic: pull your last month's carrier invoices. Calculate the average ratio of billed DIM weight to actual weight. If it's above 1.5x, you have a shipping air problem worth solving.
What Is Cartonization Software?
Cartonization software is an algorithm that takes the dimensions and weight of every item in an order, the available box sizes (and optionally envelopes), and calculates the optimal box and item arrangement. The output: which box to use, how to orient each item inside it, and how many boxes the order needs.
More advanced cartonization handles:
- Multi-box splitting. When an order doesn't fit in a single box, the algorithm decides how to split it across the fewest boxes with the lowest total DIM weight.
- Envelope routing. Small, flat items (clothing, documents, accessories) often fit in a poly mailer or padded envelope at a fraction of the box cost. Good cartonization routes these automatically.
- Diagonal rotation. Most packing algorithms only consider orthogonal placement (items aligned with box walls). Diagonal rotation considers placing items at an angle, which can mean a smaller box. Optioryx Pulse handles this, and it's one of the reasons the savings percentages are on the higher end.
- Weight distribution. For multi-item orders, placing heavy items at the bottom for stability and fragile items on top. This isn't just packing efficiency, it's damage prevention.
- Box range optimization. Analyzing your historical order data to recommend the optimal set of box sizes for your specific product mix. This is a one-time analysis that typically saves 5-8% on top of per-order cartonization.↗
Cartonization vs Pallet Stacking: Two Different Problems
Cartonization optimizes what goes inside each box. Pallet stacking optimizes how those boxes are arranged on a pallet. Both reduce transport costs, but at different levels.
Optioryx Pulse handles both cartonization and pallet stacking as connected problems. Optimizing them together means the cartonization step can consider pallet-level impact: choosing a box size that packs well on a pallet, not just one that minimizes void inside the box.
The Cartonization Software Landscape
Getting Started: How to Audit Your Shipping Air
Before investing in cartonization software, quantify your problem.
Step 1: Pull one week of shipping data. For each parcel: box dimensions used, actual product weight, billed weight from carrier, carrier cost. Most WMS and carrier systems export this.
Step 2: Calculate your DIM ratio. For each parcel: DIM weight / actual weight. Average this across all parcels. If it's above 1.3, you have a meaningful shipping air problem.
Step 3: Calculate your box fill rate. For a sample of 50-100 parcels: product volume / box internal volume. If the average is below 65%, cartonization will save you money.
Step 4: Estimate annual savings. Multiply your average DIM weight overpayment by your per-kg carrier rate by annual parcel volume. Most operations find $200K–$2M per year in recoverable cost.↗
Step 5: Run a pilot. Feed your order and product dimension data into cartonization software. Compare the recommended box selections against what you actually shipped. The gap is your savings.
Questions?
Dimensional weight (DIM weight) pricing means carriers charge based on the volume a package occupies in a vehicle, not just its actual weight. The formula: length × width × height / DIM factor (typically 5,000 for metric). If the DIM weight exceeds actual weight, you pay for the larger figure. Every major carrier (UPS, FedEx, DHL, DPD, GLS) uses DIM weight pricing, making oversized box selection a direct and measurable shipping cost driver.
Shipping air refers to the empty space inside a parcel that is still charged by the carrier through dimensional weight pricing. When a box is larger than necessary for the items it contains, the warehouse pays for the unused volume. On average, shipping air costs warehouses $2–5 per parcel in unnecessary dimensional weight surcharges. Right-sizing boxes through cartonization software eliminates shipping air and directly reduces carrier charges.
3D cartonization software calculates the best box (or combination of boxes) or different containers for an order using 3D item dimensions. In some cases it can also consider handling rules (such as "this side up" information) or carrier rates. It aims to reduce empty space, avoid repacking, and improve packing consistency and reduce transport costs.
Right-size packaging means selecting the smallest possible box or envelope that safely contains every item in an order. The goal is to minimize the volume gap between the product and the packaging — reducing dimensional weight surcharges, lowering void fill material cost, and shrinking corrugated spend. Cartonization software automates right-size box selection for every order, replacing manual judgment at the pack station with algorithmically selected box-and-placement instructions.
Cartonization specifically refers to selecting the right box and arranging items inside it to minimize parcel volume and dimensional weight charges. Packing optimization is a broader term that includes cartonization plus pallet stacking, load planning, and packaging material selection. Cartonization operates at the individual parcel level; pallet stacking operates at the outbound freight level. Systems like Optioryx Pulse handle both as connected problems — choosing box sizes that also pack efficiently onto pallets to avoid local optimization traps.
It can. Many solutions generate clear packing instructions per order (which box to use, how many cartons, suggested item placement), reducing reliance on personal experience.
Palletization helps fill warehouses and trucks more efficiently and reduces the time and labor needed to load and unload goods, which cuts transportation costs.
Yes, Pulse can link picking and packing into a single workflow, for both pick-to-box and pick-to-pallet tasks, by providing packing instructions that account for packing constraints and the optimal picking sequence.
Pulse is a warehouse optimization layer that improves how WMS tasks are executed in picking, packing, and slotting. AI-Powered algorithms cut travel by 20–50%, increase box and pallet fill rates by 10–30%, deliver data-driven slotting moves, and reduce overall labor and transport costs.
Optioryx Pulse reduces transport costs through three connected mechanisms: cartonization selects the smallest suitable box for each order, cutting dimensional weight surcharges by 15–30%; pallet stacking optimization increases parcels per pallet by 20–35%, reducing the number of outbound pallets and associated freight charges; and combined optimization ensures box selection accounts for pallet-level efficiency, avoiding tradeoffs that improve one metric while worsening another. For operations shipping thousands of parcels per day, these savings compound into significant annual cost reductions.