What is Dimensional Weight?
Dimensional weight (DIM weight) is a pricing method used by shipping carriers to calculate shipping costs based on the size of a package rather than just its actual weight. This ensures that carriers charge appropriately for large, lightweight packages that take up significant space in trucks and planes.
How DIM Weight is Calculated
The formula for calculating dimensional weight is straightforward:
DIM Weight (lbs) =
(Length × Width × Height in inches) ÷ DIM Divisor
The DIM divisor varies by carrier and service type. Your package will be charged based on whichever is greater: the actual weight or the dimensional weight.
2025 DIM Divisors by Carrier
| Carrier | Service | DIM Divisor |
|---|---|---|
| FedEx | All services | 139 |
| UPS | Daily rates | 139 |
| UPS | Retail rates | 166 |
| USPS | Packages > 1 cu ft | 166 |
| DHL | All services | 166 |
Important 2025 Update: Fractional Inch Rounding
Effective August 18, 2025
FedEx and UPS now round every fractional inch UP when measuring package dimensions for DIM weight calculations.
- •11.1 inches becomes 12 inches
- •8.01 inches becomes 9 inches
- •24.5 inches becomes 25 inches
This change can significantly increase your DIM weight and shipping costs. Precise packaging is now more critical than ever.
When Does DIM Weight Apply?
USPS
- •DIM weight only applies to packages exceeding 1 cubic foot (1,728 cubic inches)
- •Smaller packages are charged by actual weight only
FedEx, UPS, DHL
- •DIM weight applies to all packages
- •Billed weight = max(actual weight, DIM weight)
How to Reduce Your DIM Weight Costs
- •Right-size your packaging: Use the smallest box that safely fits your product. Every inch counts, especially with the new rounding rules.
- •Minimize void fill: Reduce empty space inside packages. Use appropriately sized cushioning materials.
- •Consider poly mailers: For non-fragile items, flexible poly mailers conform to product shape and reduce dimensional weight.
- •Invest in custom packaging: Custom-sized boxes designed for your specific products can significantly reduce DIM charges over time.
- •Measure accurately: Use precise measuring tools. With the new rounding rules, even 0.1" can increase your billed weight.
- •Flatten when possible: Some products can be shipped flat or partially disassembled to reduce package dimensions.
Real-World Example
Scenario: You're shipping a pillow that weighs 2 lbs in a 20" × 16" × 12" box via UPS Daily Rates (divisor: 139)
Actual Weight:
2 lbs
DIM Weight Calculation:
(20 × 16 × 12) ÷ 139 = 3,840 ÷ 139 = 27.6 lbs
Rounds to 28 lbs
Billable Weight: 28 lbs (DIM weight is greater)
You'll be charged for 28 lbs instead of 2 lbs — a 1,300% increase!
Solution: Using a 16" × 12" × 8" box instead: (16 × 12 × 8) ÷ 139 = 11.0 lbs billable weight — saving you 17 lbs in charges.
Who Should Use This Calculator?
- •E-commerce sellers: Optimize packaging to reduce shipping costs and stay competitive
- •Small business owners: Understand shipping charges before listing products
- •Fulfillment managers: Evaluate packaging options and calculate cost savings
- •Marketplace sellers: Factor DIM weight into pricing strategies on Amazon, eBay, Etsy, etc.
- •Shipping managers: Compare carriers and services based on DIM divisors
Carrier Comparison: Which Has the Best DIM Rates?
The DIM divisor directly impacts your billable weight — a higher divisor means lower DIM weight and potentially lower shipping costs for large, lightweight packages.
Better for Large Packages
- •USPS: Divisor 166, only applies to packages > 1 cu ft
- •DHL: Divisor 166
- •UPS Retail: Divisor 166
Higher DIM Charges
- •FedEx: Divisor 139, all packages
- •UPS Daily: Divisor 139, all packages
Note: While a lower DIM divisor means higher DIM weight, it doesn't always mean higher total cost. Consider base rates, fuel surcharges, and service speed when choosing a carrier.