Postal Volumetric Weight Calculator – DIM Factor for Shipping

Volumetric weight, also known as dimensional weight or DIM weight, is a pricing technique used by shipping carriers to account for the space a package occupies in their vehicles, not just its actual weight. It's calculated using the package's dimensions (length × width × height) divided by a DIM factor. If the volumetric weight exceeds the actual weight, carriers charge based on the volumetric weight — ensuring that large, lightweight packages are priced fairly for the space they consume.

The formula is straightforward:
Volumetric Weight = (Length × Width × Height) ÷ DIM Factor

Imperial example: A box measuring 20" × 15" × 10" with a DIM factor of 139:
Volumetric Weight = (20 × 15 × 10) ÷ 139 = 3,000 ÷ 139 ≈ 21.58 lbs

Metric example: A box measuring 50cm × 38cm × 25cm with a DIM factor of 5000:
Volumetric Weight = (50 × 38 × 25) ÷ 5000 = 47,500 ÷ 5000 = 9.5 kg

The carrier then charges based on the greater of volumetric weight and actual weight.

The DIM factor (also called the dimensional weight divisor) is a number set by each carrier that determines how much space equals one unit of weight. A lower DIM factor means the carrier charges more for space — your volumetric weight will be higher. A higher DIM factor is more favorable to shippers. For example, a DIM factor of 139 produces a higher volumetric weight than 166 for the same package. Carriers periodically adjust DIM factors, so it's important to stay updated. In 2017, UPS and FedEx lowered their standard DIM factor from 166 to 139, effectively increasing shipping costs for many packages.

UPS uses a DIM factor of 139 for most domestic services (Ground and Air) within the United States. For international shipments, UPS typically applies a DIM factor of 166, though this can vary by destination country and specific service level. UPS also applies dimensional weight to all packages regardless of size (since 2017), whereas previously it only applied to packages over 3 cubic feet.

FedEx uses a DIM factor of 139 for both Ground and Express domestic services in the U.S. This has been the standard since January 2017. Like UPS, FedEx applies dimensional weight pricing to all packages. For international shipments, FedEx may use different DIM factors (commonly 166) depending on the service and destination.

USPS (United States Postal Service) uses a DIM factor of 166 for Priority Mail, Priority Mail Express, and Parcel Select services. This went into effect in June 2019. USPS applies dimensional weight to packages over 1 cubic foot (1,728 cubic inches). Packages under 1 cubic foot are generally charged by actual weight only, making USPS potentially more economical for smaller packages compared to UPS or FedEx.

Here are practical ways to minimize DIM weight charges:

• Use right-sized boxes: Avoid oversized packaging. Every extra inch increases cubic volume significantly.
• Remove unnecessary void fill: While protective padding is essential, excessive fill expands package dimensions.
• Consider poly mailers or soft packaging: For non-fragile items, flexible packaging conforms to the item's actual size.
• Compare carriers: USPS (DIM 166) can be cheaper for mid-size packages than UPS/FedEx (DIM 139).
• Negotiate with carriers: High-volume shippers can sometimes negotiate better DIM factors or dimensional weight exemptions.
• Split shipments strategically: Sometimes two smaller packages cost less than one large one.

Actual weight is the physical mass of your package measured on a scale (in pounds or kilograms). Volumetric weight is a calculated value based on the package's dimensions. Carriers use the greater of the two as the billable weight. This system exists because a large box of feathers takes up significant vehicle space while weighing very little — the volumetric weight ensures the carrier is compensated for that space. Conversely, a small, dense box of books will be charged by actual weight since it weighs more than its volumetric equivalent.

No. Different carriers use different DIM factors, and even within a single carrier, factors can vary by service level and destination. The most common DIM factors are 139 (UPS/FedEx domestic standard) and 166 (USPS, many international services). Some carriers use 194 or 250 for certain services. Always check your carrier's current rate guide, as DIM factors are subject to change — carriers have been trending toward lower DIM factors (which means higher costs for shippers).

Dimensional weight pricing originated in the air freight industry decades ago. Major milestones in the U.S. parcel industry include:

• 2007: UPS and FedEx began applying DIM weight to ground packages over 3 cubic feet.
• 2015: UPS and FedEx expanded DIM weight to all ground packages (effective 2017).
• 2017: UPS and FedEx lowered their standard DIM factor from 166 to 139.
• 2019: USPS began applying DIM weight (factor 166) to packages over 1 cubic foot.

This industry-wide shift has significantly impacted shipping costs, especially for e-commerce sellers of lightweight, bulky items.

Not always. Carriers charge the greater of actual weight and volumetric weight. If your package is dense and the actual weight exceeds the volumetric weight, you'll be charged by actual weight. Additionally, some carriers have exemptions:

• USPS: Only applies DIM weight to packages over 1 cubic foot (1,728 in³). Smaller packages are charged by actual weight.
• Certain flat-rate services: USPS Flat Rate boxes, for example, aren't subject to DIM weight as long as they fit within the designated box.
• Negotiated rates: High-volume shippers may have custom agreements that modify or waive DIM weight rules.