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Dimensional weight calculator
Carriers don’t just bill by what your package weighs — they bill by how much space it takes up. Enter your box size and we’ll show the billable weight UPS, FedEx, and USPS will actually charge, so DIM weight stops surprising you at the end of the month.
Free calculator
What will this box really cost to ship?
Enter length, width, and height — or tap a preset — to see your dimensional weight for every carrier.
What dimensional weight is — and why carriers bill it
A truck runs out of space long before it runs out of weight capacity. Dimensional weight (also called volumetric weight) is how carriers charge for that space, so a big, light box can’t ride for the price of its scale weight.
The formula
Length × Width × Height ÷ the carrier’s DIM factor, rounded up. That’s your dimensional weight in pounds where dimensional pricing applies.
Billable weight wins
The carrier compares DIM weight to your actual scale weight and charges whichever is greater. That higher number is your billable weight, and it’s what your rate is built on.
The factors that matter
UPS and FedEx commercial rates use a 139 divisor; UPS retail uses 166. USPS uses 139 on eligible parcels when the volume after rounding each dimension up exceeds 1 cubic foot. A lower factor means a higher DIM weight.
Where it bites
Lightweight-but-bulky products — pillows, apparel, anything in oversized packaging — are where DIM weight quietly eats your margin, sometimes turning a 2-lb item into a 28-lb charge.
2026 DIM factors by carrier
The divisor decides how much DIM weight your box racks up. Here’s what each carrier uses today.
USPS changed its divisor from 166 to 139 on July 12, 2026.
DHL uses dimensional pricing on international shipments too — check your contract for the exact divisor. A lower factor (139) means a higher DIM weight and a higher bill than a higher factor (166).
How to calculate dimensional weight
Four steps and about a minute. Measure, find the volume, divide by the DIM factor, then take the greater of DIM weight and actual weight.
Step 1
Measure the package
Measure length, width, and height at the widest points, including any bulge in the box. UPS, FedEx, and USPS all round each dimension up to the next whole inch, so a 10.2-inch side is billed as 11. The calculator does this for you.
Step 2
Find the cubic volume
Multiply the dimensions after carrier rounding. For USPS, 12.2×10×10 inches becomes 13×10×10 = 1,300 cubic inches, so DIM weight does not apply. A 12×12×12-inch box is exactly 1,728 cubic inches and also stays below the USPS DIM trigger.
Step 3
Divide by the DIM factor
Divide the volume by your carrier's DIM factor — 139 for USPS and UPS/FedEx commercial, or 166 for UPS retail — then round up to the next whole pound. USPS only applies DIM weight when its rounded volume exceeds 1,728 cubic inches.
Step 4
Take the greater number
Round actual weight up to the next whole pound. Where DIM weight applies, take the greater of actual and DIM weight. For USPS at or below 1,728 rounded cubic inches, use rounded actual weight alone. Metric inputs convert to inches and pounds before rating; kilograms shown are equivalents of the rated pounds.
How to lower your DIM weight charges
Dimensional weight is one of the few shipping costs you can actually control — it comes down to the box, not the carrier.
Right-size the box
Most brands over-box everything. Cutting even two inches off each dimension drops the cubic volume fast. We see right-sizing alone trim shipping costs 15–20% overnight.
Use poly mailers
If the product isn’t fragile, skip the box. Mailers are measured at their actual, thin dimensions, so the scale weight usually wins instead of DIM weight.
Cut the void fill
Air pillows and crumpled paper inflate the box you need. Less filler means a smaller carton, a smaller DIM weight, and a smaller bill.
Negotiate your factor
Shipping 500+ packages a month? Carriers can bump your DIM factor from 139 toward 166, which lowers DIM weight on bulky shipments. Most brands don’t know it’s negotiable.
Tired of DIM weight eating your margin?
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We right-size every box, route each order to the cheapest carrier, and handle the DIM-weight math on our end — then bill you flat-rate by simple weight tiers. No zone spreadsheets, no surprise surcharges. Just a predictable cost per order out of our Austin, TX warehouse.
Dimensional weight FAQs
- What is dimensional weight?
- Dimensional weight (DIM weight, sometimes called volumetric weight) is a pricing method carriers use to charge for the space a package takes up, not just what it weighs. If a box is large but light, the carrier prices it on its size instead of the scale reading — so a 2-lb pillow in a big box can cost like a 28-lb shipment.
- How do I calculate DIM weight?
- For USPS, round each dimension up to the next whole inch, then multiply length × width × height. If the rounded volume exceeds 1,728 cubic inches, divide by 139 and round up to the next whole pound. Otherwise, DIM weight does not apply. A 14×12×12-inch USPS parcel is 2,016 cubic inches; 2,016 ÷ 139 ≈ 14.50, rounded up to 15 lb. UPS and FedEx commercial shipments use 139; UPS retail uses 166.
- What is billable weight?
- Billable weight is the number your shipping rate is actually based on. The carrier compares your package's DIM weight to its actual (scale) weight and charges whichever is greater. For USPS, round actual weight up to the next whole pound and compare it with DIM weight only when the rounded volume exceeds 1,728 cubic inches; otherwise, billable weight is the rounded actual weight.
- Do UPS, FedEx, USPS, and DHL all use dimensional weight?
- UPS, FedEx, and DHL apply DIM pricing to essentially every package. USPS applies it to eligible Priority Mail Express, Priority Mail, USPS Ground Advantage and Parcel Select parcels, at retail and commercial rates, only when the volume after rounding each dimension up exceeds one cubic foot (1,728 cubic inches), and USPS Flat Rate boxes are exempt. The carriers use different divisors, which is why the same box can be billed at a different weight depending on who you ship with.
- How do I lower my dimensional weight charges?
- Right-size the box — even shaving two inches off each dimension cuts the cubic volume and the DIM weight noticeably. Use poly mailers instead of boxes for non-fragile items, since they're measured thin enough that actual weight usually wins. Cut excess void fill. And if you ship 500+ packages a month, ask your carrier to negotiate a higher DIM factor (for example 139 to 166), which lowers DIM weight on bulky shipments.
- Why did my shipping cost more than expected?
- It's almost always dimensional weight. If your package is large relative to what it weighs, the carrier billed you on its dimensions rather than the scale. Run the box through the calculator above to see your real billable weight before you ship.