Dimensional Weight Calculator: Master DIM Pricing
Carriers charge based on package size OR weight - whichever is greater. Understanding dimensional weight is essential to avoiding surprise shipping charges.
How do you calculate dimensional weight?
Dimensional weight = (Length x Width x Height) / DIM factor. DIM factors by carrier: USPS = 166, UPS = 139, FedEx = 139, DHL = 139. Example: A 12x10x8" box = 960 cubic inches / 139 = 6.9 lbs DIM weight. If your box weighs 3 lbs actual, you pay for 7 lbs.
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| Carrier | Service | Price | Delivery Time | |
|---|---|---|---|---|
| USPS | DIM Factor | 166 | Cubic inches ÷ 166 | |
| UPS | DIM Factor | 139 | Cubic inches ÷ 139 | |
| FedEx | DIM Factor | 139 | Cubic inches ÷ 139 | |
| DHL Express | DIM Factor | 139 | Cubic inches ÷ 139 | Cheapest |
DIM Factor
DIM Factor
DIM Factor
DIM Factor
* Prices shown are discounted ShipWave rates. Actual rates vary by exact dimensions, weight, and origin/destination.
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Understanding Dimensional Weight
Why DIM weight exists: Carriers have limited space. A large, light package takes as much truck/plane space as a small, heavy one. DIM weight ensures shippers pay for the space they use.
Billable weight: Carriers compare actual weight to DIM weight and charge whichever is greater. A 2 lb package in a huge box might be billed as 10 lbs.
DIM factor: The divisor used to convert cubic inches to pounds. Lower DIM factor = higher DIM weight = more cost. UPS/FedEx (139) charge more for large boxes than USPS (166).
DIM Weight Formulas by Carrier
USPS formula: (L x W x H) ÷ 166 = DIM weight. USPS is most forgiving for large, light packages. Only applies to Priority Mail packages over 1 cubic foot.
UPS/FedEx formula: (L x W x H) ÷ 139 = DIM weight. Applies to all packages. These carriers are stricter - right-sizing boxes is crucial.
DHL formula: (L x W x H) ÷ 139 for domestic, or (L x W x H in cm) ÷ 5000 for international = DIM weight in kg.
Optimizing Packages for DIM Weight
Right-size every package: Use the smallest box that safely fits your product plus padding. Every extra inch of air costs money.
Consider flat items: A flat package (14x10x2") has much lower DIM weight than a cube (8x8x8") despite similar volume.
Use poly mailers when possible: For soft goods, poly mailers virtually eliminate DIM weight concerns. Carriers measure the collapsed mailer dimensions.
Pro Tips to Save More
Always Calculate Before Shipping
Know your DIM weight before choosing a carrier. It can dramatically change which option is cheapest.
Round Up Your Measurements
Carriers round dimensions up. A 10.2" dimension is charged as 11". Measure precisely.
Use USPS for Large, Light Packages
USPS has the most favorable DIM factor (166). For big, light items, USPS often wins.
Stock Multiple Box Sizes
Having 3-4 box sizes lets you match packages to products efficiently.
Consider Flat Rate Boxes
Carrier flat rate options ignore DIM weight entirely - pay one price regardless of size.
Measure the Actual Shipped Box
Bulging boxes or tape adding thickness increases your billed dimensions.
Frequently Asked Questions
- USPS: Only Priority Mail packages over 1 cubic foot (1,728 cubic inches). UPS/FedEx: All packages regardless of size. Ground services often have a minimum billable weight of 1 lb.
- Likely DIM weight. A package measuring 18x12x10" weighs 15.5 lbs in DIM weight even if the contents weigh only 5 lbs. You pay for 16 lbs.
- Use smaller boxes that closely fit your products. Remove excess void fill. Consider poly mailers for soft goods. Compare USPS (DIM factor 166) vs UPS/FedEx (139) for large items.
- No. USPS Priority Mail Flat Rate, UPS Simple Rate, and FedEx One Rate boxes are charged a flat price regardless of size or weight (within carrier limits).
- Measure the longest point of each dimension (length, width, height) of the outside of the box. Include any bulges or protrusions. Carriers round up to the next inch.
- Lower DIM factor = higher shipping cost for large packages. A 12x12x12" box: At 139 = 12.4 lbs, at 166 = 10.4 lbs. That is a 2 lb difference in billable weight.
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