Shipping Cost Calculator
Find the true billable weight a carrier will charge for your package by comparing actual weight against dimensional (DIM) weight — enter your package's
Shipping Cost Calculator
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Formula: DIM Weight = L×W×H / 139 (USPS/UPS/FedEx) | Billable = max(Actual, DIM)
Worked example — Billed at 25.9 lbs
Formula
DIM Weight = L×W×H / 139 (USPS/UPS/FedEx) | Billable = max(Actual, DIM)
Carriers charge by whichever is greater: actual weight or dimensional weight. DIM divisor: 139 for domestic, 166 for international.
Worked Examples
Example 1: Light large box
Problem:2 lbs, 20×15×12 inches
Solution:DIM = 20×15×12/139 = 25.9 lbs → billed at 25.9
Result:Billed at 25.9 lbs
Example 2: Heavy compact box (actual weight wins)
Problem:35 lbs, 14×12×10 inches
Solution:DIM = 14×12×10/139 = 12.1 lbs. Actual (35 lbs) exceeds DIM, so billable = max(35, 12.1)
Result:Billed at 35 lbs (actual weight governs)
Frequently Asked Questions
What is dimensional weight?
Carriers charge for the space a package occupies, not just its weight. Light but large packages are charged by DIM weight (L×W×H/139).
Why do carriers use 139 as the DIM divisor for domestic shipments?
The divisor of 139 cubic inches per pound is the standard used by UPS, FedEx, and USPS for domestic US shipments. For international shipments, the divisor is typically 166 cubic inches per pound, which is the imperial expression of 6,000 cubic centimetres per kilogram; the metric equivalent of 139 is 5,000 cubic centimetres per kilogram. A lower divisor increases DIM weight, making it easier for carriers to charge volumetric rates on bulky packages.
How can I reduce shipping costs when DIM weight is higher than actual weight?
Use the smallest box that safely fits your product, eliminate unnecessary void fill, consider flexible poly mailers for soft goods, and consolidate multiple items into one shipment. Some carriers offer flat-rate boxes where DIM weight is irrelevant — useful for dense, heavy items in small packages. Custom or right-sized packaging can dramatically reduce billable weight.
What is the girth calculation used for?
Girth (2×width + 2×height) plus length is used by USPS to check size limits. USPS caps length plus girth at 130 inches on most domestic Priority Mail packages, while UPS and FedEx use their own combined limits and apply oversize handling above them. Exceeding these limits results in returned packages or oversized surcharges even if DIM weight is acceptable.
Should I use the domestic (139) or international (166) DIM divisor?
Use 139 for shipments within the United States via UPS, FedEx, or USPS Priority Mail — this is the standard domestic divisor as of the carriers' current rate guides. Use 166 for international shipments and for USPS First-Class Package International Service, since the international standard treats a cubic inch of space as less costly per pound, producing a lower DIM weight for the same box. Always confirm the specific carrier and service tier's current divisor before shipping high-volume or oversized freight, since carriers periodically revise these figures.
Why did my invoice charge more than Shipping Cost Calculator's billable weight suggests?
Beyond dimensional weight, carriers layer on additional per-package surcharges that Shipping Cost Calculator does not model directly: residential delivery fees, fuel surcharges (a percentage added on top of the base rate that fluctuates with oil prices), signature confirmation, and additional handling fees for packages that are oddly shaped, poorly packaged, or exceed size thresholds (over 96 inches in length, for instance). The billable weight from Shipping Cost Calculator is the starting point carriers use to look up the base rate on their published rate chart — the final invoice total adds these surcharges on top.
How do I convert between a metric volumetric divisor and the 139 or 166 figure?
Multiply the metric divisor in cubic centimetres per kilogram by 0.45359 kg per pound, then divide by 16.387 cubic centimetres per cubic inch. A divisor of 5,000 cm3/kg works out at about 138 cubic inches per pound, which is where 139 comes from, and 6,000 cm3/kg converts to about 166 cubic inches per pound. A quoted divisor is meaningless without its units, so confirm whether a carrier's published figure is metric or imperial before comparing two rate sheets.
At what package density does DIM weight start to exceed actual weight?
The divisor is itself the break-even density, read as cubic inches per pound. With a divisor of 139, any package occupying more than 139 cubic inches per pound of actual weight will be billed on dimensional weight. A 10 lb parcel is therefore DIM-billed once its cube passes 1,390 cubic inches. Comparing your parcel's cube-per-pound with the divisor tells you instantly which side of the threshold you are on, and how much you would need to shrink the box to cross back.
What is the difference between an oversize surcharge and dimensional weight?
Dimensional weight is a pricing mechanism: it converts bulk into a billable weight that is then rated normally. An oversize or additional-handling surcharge is a separate flat fee triggered when a package crosses a threshold on length, on length plus girth, or on actual weight, because it can no longer run through automated sortation. The two apply independently, so a large light parcel can be rated on DIM weight and still collect a handling fee on top.
How does rounding of dimensions and weight change the billable figure?
Carriers measure each dimension at its widest point, including bulges and protruding packaging, and the rounding rule is carrier-specific: some published tariffs round each measurement to the nearest whole inch, others round every fraction upward, and the resulting dimensional weight is then usually taken up to the next whole pound. Because rounding is applied at several stages it compounds, so a box sitting a fraction above a boundary on two sides can gain a pound or more of billable weight. Read the measuring rule in your carrier's rate guide first, then trim the packaging so each finished outer dimension falls below whichever boundary that rule actually uses.
References
Reviewed for accuracy by Daniel Agrici, Founder & Lead Developer · Editorial policy
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