Carton Cube Utilization, Void Fill and Dim Weight Calculator
Shipping air is expensive twice: you buy void fill and you pay freight on volume. This calculator measures how full a carton is and shows whether dimensional weight is driving the freight bill.
Your numbers
Your results
Uses bounding boxes for product volume and a simple carrier formula. Check your carrier contract for rounding rules and minimum charges.
Dimensional and billable weight vs carton height
Sweeps Carton inside height from 100 to 500, holding your other inputs fixed.
Carton right-sizing review
Optional review of how to analyse carton usage and freight cost from your ERP shipment data.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the inside carton size, the size of one product, units per carton and packed weight. Pick the carrier divisor and enter void fill and freight costs. You get utilization, void volume, void-fill cost, dimensional weight and billable weight. Use the chart to see where a taller carton moves from weight-based billing to volume-based billing, then try a smaller carton size.
The formulas
Cube utilization is product volume divided by carton volume. Void volume is the difference. Dimensional weight is carton volume in cubic centimetres divided by the carrier divisor, such as 5000 cm3 per kg. The carrier bills the larger of actual weight and dimensional weight. Dim weight uses the outer dimensions of the package, so allow for board thickness if you use inside dimensions as a proxy.
- Utilization = product volume / carton volume
- Void = carton volume - product volume
- Dim weight = L x W x H in cm3 / divisor
- Billable = max(actual, dim weight)
Common mistakes
Using inside dimensions when the carrier measures outside underestimates dim weight slightly. Also, bounding-box volume overstates product volume for irregular shapes, which can make utilization look better than reality. Reducing carton size can hurt protection, so test drops and vibration before changing specs. Check whether your carrier rounds each dimension up to a whole centimetre or inch.
- Use outer dimensions for dim weight when possible
- Test protection after right-sizing
- Check rounding rules in the carrier contract
- Review the carton range, not just one size
Frequently Asked Questions
What is dimensional weight?
It is a pricing weight that reflects the space a package takes, calculated from its dimensions and a carrier divisor. If it exceeds actual weight, the carrier charges on dimensional weight instead.
Which divisor should I use?
Use the one in your carrier contract. Values like 5000 or 6000 cm3 per kg are common in international and freight use, while US carriers often quote cubic inches per pound. Check your rate card.
What utilization is good?
There is no universal target because protection needs differ. Rigid, stackable goods can reach a high fill, while fragile items need cushioning. Compare cartons within the same product family.
Does void-fill cost matter that much?
Per carton it is small, but across thousands of shipments it adds up, along with higher freight and storage space. Right-sizing usually saves more through freight than through fill material.
We can help you run this across your whole item and carton master in your ERP to find the cartons costing you most.
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