Dimensional Weight: How Couriers Turn Box Size into Billable Kilograms and Pounds

If you have ever shipped a pillow, a lampshade or an empty-looking box and been charged far more than its weight suggested, you have met dimensional weight (also called DIM weight or volumetric weight). Couriers sell space in trucks and aircraft, and a large, light parcel takes up as much space as a heavy one. Dimensional weight converts the size of a box into an equivalent weight so the carrier can bill for that space.

Billable weight: the larger of two numbers

Every parcel has two weights:

• Actual weight – what the scale says.
• Dimensional weight – the box volume divided by a carrier "divisor".

The carrier charges for whichever is larger. That figure is the billable weight.

The formula in inches and pounds

DIM weight (lb) = Length × Width × Height (in) ÷ 139

In 2026 the 139 divisor is the standard for UPS daily rates and FedEx in the United States, and USPS adopted the same divisor in July 2026, replacing its previous 166. Carriers typically round each fractional dimension up to the next whole inch and round the result up to the next whole pound.

Example: a box measuring 16 × 12 × 10 inches that weighs 6 lb.

• Volume: 16 × 12 × 10 = 1,920 cubic inches
• DIM weight: 1,920 ÷ 139 = 13.81 → 14 lb
• Billable weight: the larger of 6 lb and 14 lb = 14 lb

You pay for 14 pounds even though the scale shows 6.

The formula in centimeters and kilograms

DIM weight (kg) = Length × Width × Height (cm) ÷ 5,000

International express services from DHL, FedEx and UPS generally use 5,000 cubic centimeters per kilogram. Some economy or freight services use 6,000, which produces a lower dimensional weight, and negotiated accounts may have their own divisor – always confirm the figure in your carrier's service guide.

Example: a box of 50 × 40 × 30 cm weighing 4 kg.

• Volume: 50 × 40 × 30 = 60,000 cm³
• DIM weight: 60,000 ÷ 5,000 = 12 kg (with a 6,000 divisor: 10 kg)
• Billable weight: 12 kg, about 26.5 lb

Why 139 and 5,000 are the same rule

The two divisors look unrelated, but they describe almost the same density. One cubic inch is 16.387064 cm³ and one kilogram is 2.20462 lb. Converting 5,000 cm³ per kg into imperial units:

• 5,000 ÷ 16.387064 = 305.1 cubic inches per kilogram
• 305.1 ÷ 2.20462 = 138.4 cubic inches per pound

So a carrier using 139 in the US and 5,000 abroad is applying essentially one rule in two unit systems. Our first example confirms it: the 16 × 12 × 10 inch box is 40.64 × 30.48 × 25.4 cm = 31,462 cm³, which gives 6.29 kg – about 13.9 lb, matching the 13.81 lb from the imperial formula. Use the length converter and weight converter when your supplier quotes dimensions in one system and your carrier bills in the other.

Quick reference

How to reduce dimensional weight

• Use the smallest box that protects the item. Shrinking the example box to 14 × 10 × 8 inches cuts the volume to 1,120 in³ and the DIM weight to 9 lb – five billable pounds less.
• Measure correctly. Measure the longest point of each side, including bulges. Carriers re-measure parcels automatically and add a correction fee if your declared size is too small.
• Use poly mailers for soft goods such as clothing, which don't need a rigid box.
• Compare divisors. If you ship a lot of light, bulky products, ask about services or contracts with a higher divisor.

Dimensional weight is also a cost of importing inventory. Our sister site Feexio shows how freight fits into the landed cost per unit of imported products.