Dimensional Weight Pricing: How DIM Weight Affects Your Shipping Costs

Dimensional weight (DIM weight) pricing ensures carriers are compensated fairly for large, lightweight packages that take up valuable space. Understanding DIM weight helps you avoid surprise charges and optimize your shipping costs.

What is Dimensional Weight?

Dimensional weight is a pricing technique that considers package size, not just actual weight. Carriers compare DIM weight to actual weight and charge based on whichever is greater.

The concept: A large box of pillows weighs 2 lbs but takes the same truck space as a 15 lb box of books. DIM weight pricing charges the pillow box based on its size, not weight.

How to Calculate DIM Weight

The Formula

DIM Weight = (Length × Width × Height) ÷ DIM Factor

DIM Factors by Carrier

Note: Lower DIM factor = higher DIM weight = higher cost

Calculation Example

Package dimensions: 18" × 14" × 10" Actual weight: 5 lbs

UPS/FedEx (DIM factor 139):

• Volume: 18 × 14 × 10 = 2,520 cubic inches
• DIM weight: 2,520 ÷ 139 = 18.1 lbs (rounds to 19 lbs)
• Billable weight: 19 lbs (DIM weight higher than actual)

USPS (DIM factor 166):

• DIM weight: 2,520 ÷ 166 = 15.2 lbs (rounds to 16 lbs)
• Billable weight: 16 lbs (still DIM weight)

When DIM Weight Applies

UPS

• All services for packages over 1 cubic foot (1,728 cubic inches)
• Some services for all package sizes

FedEx

• All services for packages over 1 cubic foot
• Express services may have different thresholds

USPS

• Priority Mail for packages over 1 cubic foot
• Ground Advantage for packages over 1 cubic foot
• First-Class Mail exempt (max size limits apply)

Impact on Shipping Costs

Example: Large, Light Package

20" × 16" × 12" box weighing 4 lbs

This is why packaging optimization is crucial!

Strategies to Reduce DIM Weight Impact

1. Right-Size Your Packaging

Use the smallest box that safely fits your product.

2. Use Poly Mailers When Possible

For non-fragile items, poly mailers eliminate DIM weight entirely:

• No height dimension
• Based on actual weight only
• Cheaper materials cost

3. Consider USPS for Large, Light Items

USPS's higher DIM factor (166 vs 139) means lower DIM weights:

• 19% lower DIM weight than UPS/FedEx
• Can result in significant savings

4. Evaluate Flat Rate Options

USPS Flat Rate boxes ignore dimensions:

• Small Flat Rate Box: $10.40 any weight
• Medium Flat Rate Box: $17.10 any weight
• Large Flat Rate Box: $22.45 any weight

Compare: If your DIM weight pushes Priority Mail over $17, the Medium Flat Rate might be cheaper.

5. Use Priority Mail Cubic

For dense, heavy items in small boxes:

• Based on cubic size tiers, not weight
• Up to 20 lbs with no weight penalty
• Often cheaper than DIM-adjusted rates

Packaging Optimization Tips

Choose Appropriate Box Sizes

Stock various box sizes:

• Extra small (6×4×4)
• Small (8×6×4)
• Medium (12×9×6)
• Large (18×12×8)

Match product to closest fit.

Reduce Void Fill

Less void fill needed = smaller box possible:

• Use form-fitting inserts
• Consider custom boxes for high-volume SKUs
• Evaluate product bundling

Rethink Product Design

For new products:

• Design for shipping efficiency
• Consider collapsible/flat-pack options
• Minimize packaging dimensions

DIM Weight Calculator

Use this quick reference:

Carrier Comparison for Large Packages

For a 24×18×12 box (5,184 cu in) weighing 8 lbs:

USPS wins due to better DIM factor—but always compare!

AtoShip DIM Weight Features

AtoShip automatically:

• Calculates DIM weight based on entered dimensions
• Shows billable weight for each carrier
• Compares rates using correct billable weights
• Identifies savings from alternative packaging

Common DIM Weight Mistakes

1. Ignoring Dimensions

Don't just enter weight—always include accurate dimensions for proper rate comparison.

2. Using Standard Box When Smaller Works

Defaulting to one box size leaves money on the table.

3. Not Comparing Carriers

DIM factors differ—the cheapest option varies by package.

4. Forgetting About Flat Rate

Sometimes Flat Rate beats DIM-adjusted rates.

5. Overlooking Poly Mailers

If the product can ship in a mailer, you eliminate DIM entirely.

Conclusion

Dimensional weight pricing significantly impacts shipping costs for large, light packages. By understanding how DIM weight is calculated and implementing packaging optimization strategies, you can reduce shipping expenses substantially.

Key takeaways:

• USPS has more favorable DIM factor (166 vs 139)
• Right-size packaging is the biggest opportunity
• Flat Rate can beat DIM-adjusted rates
• Always enter dimensions for accurate rate comparison

Use AtoShip to automatically calculate DIM weight and find the best rate for every package.