Dimensional weight calculator
Parcel carriers bill the greater of what a box weighs and how much space it takes up. Enter your box sizes and weights to see the DIM weight, the billable weight, and whether a smaller box would save you money.
Short answer: Dimensional (DIM) weight = length × width × height in inches, each side rounded to the nearest inch, divided by the carrier's DIM divisor and rounded up to the next pound. Most parcel carriers use 139 for commercial rates; some domestic retail rates use 166. You're billed on whichever is greater, the DIM weight or the actual weight.
Your packages
139 is the divisor most parcel carriers use for commercial and daily-rate shipping. 166 shows up on some domestic retail rates. Contract rates can use a different number, so check yours.
Billable weight
18 × 14 × 12 in = 3,024 cu in ÷ 139 = 21.76, rounded up to 22 lb.
Billed on DIM. A box 1 inch smaller on every side would cut billable weight by about 4 lb.
Sides are rounded to the nearest inch. Carriers’ divisors, rounding and large-package rules vary and change, so check your carrier’s current rules before you ship.
How parcel DIM weight is calculated
Measure and round
Measure the longest side as length, then width and height, at the widest points including any bulge. Round each side to the nearest whole inch.
Cubic inches ÷ divisor
Multiply the three sides to get cubic inches, then divide by the divisor. A lower divisor produces a higher DIM weight, so 139 bills more than 166.
Round up
Round the DIM weight up to the next whole pound. Actual weight with a fraction is rounded up the same way.
Bill the greater
Billable weight is the higher of DIM and actual weight, figured per package. A multi-box shipment adds up each box's billable weight.
An 18 × 14 × 12 inch box that weighs 8 lb
Using the 139 divisor
- Cubic inches:
18 × 14 × 12 = 3,024 - DIM weight:
3,024 ÷ 139 = 21.76, rounded up to22 lb - Actual weight:
8 lb - Billable weight: the greater of 22 and 8, so
22 lb
With the 166 divisor the same box works out to 3,024 ÷ 166 = 18.22, or 19 lb. Either way you pay for far more than the 8 lb on the scale.
Move the same product into a 16 × 12 × 10 inch box and the DIM weight at 139 drops to 1,920 ÷ 139 = 13.81, or 14 lb. That is 8 billable pounds saved on every shipment of that item.
Frequently asked questions
What is dimensional weight?
Dimensional weight is a billing weight based on a package's size rather than its scale weight. It keeps light, bulky boxes from riding for the price of a small heavy one, since both take up space in the truck or plane.
What DIM divisor should I use?
Use the divisor in your carrier agreement. Most parcel carriers use 139 for commercial and daily rates, and 166 appears on some domestic retail rates. Negotiated contracts sometimes carry a higher divisor, which lowers DIM weight. Divisors change, so confirm your carrier's current number.
Do carriers round each dimension?
Most parcel carriers round each measurement to the nearest whole inch before multiplying, then round the DIM result up to the next pound. Rules can differ by carrier and service, so check your carrier's current guide.
Does DIM weight apply to small packages?
Under most parcel carriers' current rules, yes: DIM pricing applies to packages of every size. Some carriers and services have used minimum size or cubic thresholds in the past, so check the rules for the service you use.
How can I lower my DIM weight?
Right-size your boxes. Shaving an inch off each side of a mid-size box can drop several billable pounds, and the savings repeat on every shipment. Avoid oversized void fill, and ask whether your volume qualifies for a negotiated divisor.
Is this the same as freight class or LTL density?
No. Parcel DIM weight sets a billable weight per package. Pallet freight is priced differently, by weight, density-based class and space on the trailer. For pallets, try the pallet and trailer space calculator or request a freight quote.
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