Find billable dimensional weight from package dimensions, compare it to actual weight, and see which one you'll be charged on.
Calculator verified • Last updated: August 2026
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Dimensional (DIM) weight converts a package's volume into an equivalent weight, so carriers can charge fairly for space-hungry-but-light packages. The formula divides the package's cubic size by a carrier-specific divisor:
$$\text{DIM Weight (lbs)} = \frac{L \times W \times H \text{ (in)}}{\text{Divisor}}$$
L, W, H: the package's length, width, and height, in inches.
Divisor: a carrier- and service-specific constant — commonly 139 or 166 for US domestic shipping in inches and pounds, though it varies. International air freight commonly uses a metric version with a divisor like 5000 or 6000 (centimeters and kilograms).
Whichever is higher — dimensional weight or actual scale weight — is what the carrier bills you for. That's why a large box of pillows can cost more to ship than its actual weight would suggest: it's being charged for the truck or plane space it occupies, not just what it weighs on a scale.
A 20 × 16 × 12 inch box weighing 8 lbs on a scale: volume = 20 × 16 × 12 = 3,840 in³. At a divisor of 139: dimensional weight = 3,840 ÷ 139 ≈ 27.6 lbs. Since 27.6 lbs (dimensional) is higher than 8 lbs (actual), the carrier bills this shipment as roughly 28 lbs — more than three times its actual weight, purely because of how much space it takes up.
Unlike a physics constant, the DIM divisor is a business decision each carrier sets (and periodically changes) for each service level — ground vs. air, domestic vs. international, and different carriers entirely. A lower divisor produces a higher dimensional weight for the same box, so carriers lowering their divisor over time (as several major carriers have done) effectively raises billed weight on large, light packages. Because these numbers change and vary by carrier, always confirm the current divisor with your specific carrier and service before using dimensional weight to estimate real shipping costs — the values in this calculator are commonly cited reference points, not a guarantee of what any specific carrier will charge.
The most direct lever is packaging size: a box with less empty air space around the product has a smaller L×W×H product and therefore a lower dimensional weight, even carrying the identical item. Choosing the smallest box that safely fits a shipment — rather than reusing an oversized box on hand — is the single most effective way to reduce DIM-weight charges on light, bulky items.
Billable Weight — the weight a carrier actually charges for: whichever is greater, actual weight or dimensional weight.
DIM Divisor — the carrier- and service-specific constant used to convert cubic volume into an equivalent weight.
Volumetric Weight — another common name for dimensional weight, especially in international/air freight contexts.
It depends on your carrier and service level — 139 (inches, lbs) is a commonly used US domestic divisor for several major carriers today, though 166 is still used for some services, and international air freight commonly uses 5000 or 6000 (cm, kg). Always confirm the exact divisor with your specific carrier and service, since it varies and changes over time.
Carriers bill on whichever is higher — actual weight or dimensional weight. This calculator shows both so you can see which one your shipment will actually be charged on.
A large, lightweight box (packing peanuts, an empty-looking oversized package) takes up truck and plane space out of proportion to its actual weight. Dimensional weight pricing charges for that space, not just the weight on a scale.