What Is Dimensional Weight? (And How It’s Costing You Money)
If you’ve ever been surprised by a shipping invoice that charged more than you expected, dimensional weight might be the culprit. Understanding how it works — and how to manage it — can save your business significant money every single month.
The Short Answer
Dimensional weight (also called DIM weight or volumetric weight) is a pricing method used by major carriers like UPS, FedEx, and USPS to account for the space a package takes up in a truck or aircraft, not just how heavy it is.
The idea is simple: a large, lightweight box takes up just as much room as a heavy one. Carriers don’t want to be paid only for weight when bulky packages are filling up their vehicles. So they invented dimensional weight — a calculated “theoretical weight” based on the size of your box.
You’re then charged for whichever is greater: the actual weight or the dimensional weight.
How Is Dimensional Weight Calculated?
The formula is straightforward:
Dimensional Weight = (Length × Width × Height) ÷ DIM Factor
The DIM factor (also called the divisor) varies by carrier and shipping method:
| Carrier | Domestic DIM Factor | International DIM Factor |
|---|---|---|
| UPS | 139 | 139 |
| FedEx | 139 | 139 |
| USPS Priority Mail | 166 | 166 |
| DHL Express | 139 | 139 |
Example: A box measuring 18″ × 14″ × 12″ has a volume of 3,024 cubic inches. Divide by 139 and you get a dimensional weight of 21.75 lbs — rounded up to 22 lbs. If your actual product only weighs 5 lbs, you’ll still be billed for 22 lbs.
Why Does Dimensional Weight Matter for Your Business?
For e-commerce brands and online retailers, dimensional weight is one of the most overlooked shipping costs. Many businesses choose boxes based on what fits — without considering how carriers will price the shipment.
Here’s where it hits hardest:
Lightweight but bulky products — think pillows, candles in gift boxes, clothing, toys, or anything packaged with a lot of void fill — are the biggest victims of DIM weight pricing. A candle that weighs 1 lb shipped in a 12″ × 10″ × 8″ box has a DIM weight of nearly 7 lbs. That’s 7x the actual weight — and 7x the base rate.
Incorrect box sizing is the most common and most fixable cause of dimensional weight overcharges. Using the right-sized box for each SKU is the single most impactful change most shippers can make.
How to Reduce Your Dimensional Weight Costs
1. Right-size your packaging
Use boxes that closely match the dimensions of your product. Every unnecessary inch of space increases your DIM weight and your shipping bill. A box that’s even 2 inches larger on each side can add several pounds of billable weight.
2. Audit your current packaging
Run an audit of your top-selling SKUs. For each one, calculate the actual weight vs. the DIM weight being charged. You may be surprised how many are billed on DIM weight rather than actual weight.
3. Consider poly mailers or padded mailers
For soft goods, apparel, and lightweight items, poly mailers have very low DIM weight because they conform to the shape of the product. Switching from a box to a mailer where appropriate can cut shipping costs dramatically.
4. Use variable box sizing
Rather than packing everything into one or two standard box sizes, invest in a range of sizes that match your products more closely. Many fulfillment operations see meaningful cost reductions just from expanding their box assortment.
5. Work with a packaging expert
A packaging partner like Packizon can help you analyze your shipping data, recommend optimal box sizes and materials, and even design custom packaging that minimizes DIM weight while keeping your products protected and your unboxing experience on-brand.
A Quick Reference: Actual Weight vs. Dimensional Weight
| Scenario | Actual Weight | DIM Weight | Billed Weight |
|---|---|---|---|
| Dense, compact item | 15 lbs | 8 lbs | 15 lbs (actual) |
| Light, bulky item | 3 lbs | 18 lbs | 18 lbs (DIM) |
| Well-sized packaging | 6 lbs | 6 lbs | 6 lbs (equal) |
The goal is to close the gap between actual weight and DIM weight. When they’re equal — or when actual weight is higher — you’re not leaving money on the table.
The Bottom Line
Dimensional weight isn’t going away. Carriers introduced it to better reflect the true cost of moving packages through their networks, and it now applies to virtually all ground and air shipments above a certain size.
The good news? It’s one of the most actionable shipping costs you can control. With smarter packaging choices, the right box assortment, and a partner who understands the nuances of carrier pricing, you can meaningfully reduce what you spend on shipping — without sacrificing protection or presentation.
At Packizon, we help brands ship smarter. Whether you’re shipping 100 orders a month or 100,000, we’ll help you find packaging solutions that keep your products safe, your customers happy, and your shipping costs where they belong.
Ready to reduce your dimensional weight costs? Get in touch with the Packizon team to learn how we can help.