Question 1

What is dimensional weight?

Accepted Answer

Dimensional weight, also called volumetric weight or DIM weight, is a pricing figure that converts the space a parcel occupies into a weight value. Carriers sell trailer and aircraft space, not just mass, so a large but light box is charged as though it were heavier. You are billed on whichever is greater, the dimensional weight or the actual scale weight.

Question 2

How do I calculate dimensional weight?

Accepted Answer

Multiply length by width by height to get the cubic volume of the parcel, then divide that volume by the carrier's dimensional divisor. In imperial units the result is in pounds, using inches and a divisor such as 139 or 166. In metric units the result is in kilograms, using centimetres and a divisor such as 5000 or 6000. Round the final billable figure up to the next whole unit.

Question 3

What is a DIM divisor or dimensional factor?

Accepted Answer

The DIM divisor is the number a carrier uses to convert cubic volume into a weight value. A lower divisor produces a higher dimensional weight and therefore a higher charge. Divisors are set in each carrier's published rate tariff and in negotiated contracts, so a high volume shipper may hold a more favourable divisor than the published retail figure.

Question 4

Why is my shipping cost higher than the weight on my scale?

Accepted Answer

Because the parcel was billed on dimensional weight rather than scale weight. This happens when the box is oversized relative to its contents, most often from excess void fill, a carton chosen for convenience rather than fit, or protective packaging that adds bulk without mass. The gap between the two figures is the DIM penalty.

Question 5

What is the difference between the 139 and 166 divisors?

Accepted Answer

Both convert cubic inches into pounds, but 139 is the more aggressive figure and produces a higher billable weight for the same box. A 12 by 12 by 12 inch carton is 1,728 cubic inches, which is roughly 12.43 pounds at 139 and roughly 10.41 pounds at 166. Confirm which divisor applies to your account, since it varies by service level and by contract.

Question 6

How is volumetric weight calculated in metric units?

Accepted Answer

Multiply length by width by height in centimetres, then divide by the volumetric divisor to get kilograms. International express services commonly use 5000, while some standard and economy parcel services use 6000. The higher divisor produces a lower volumetric weight for the same carton.

Question 7

What is length plus girth and why does it matter?

Accepted Answer

Girth is twice the width plus twice the height, measured around the parcel at its thickest point perpendicular to the longest side. Length plus girth is the standard measure carriers use to define oversize thresholds. Crossing a threshold can trigger a large package surcharge, and crossing the upper limit can make the parcel ineligible for standard parcel service altogether, pushing it to freight.

Question 8

How can I reduce dimensional weight charges?

Accepted Answer

Cut cubic volume before you cut anything else. Right size the carton to the product, reduce void fill, use mailers or poly bags where protection allows, flat pack or nest components, and audit your most shipped SKUs for boxes that are one size too large. Negotiating a higher divisor with the carrier is the second lever, and it is usually only available at volume.

Question 9

Do carriers apply dimensional weight to every parcel?

Accepted Answer

Most major parcel carriers apply dimensional weight to ground and express shipments across the size range, though the exact scope, divisor and any small package exemptions differ by carrier, service and region. Check the current published tariff for the specific service you are booking rather than assuming a single rule applies everywhere.

Divisor	Units	Typical use
139	in → lb	Commercial parcel, express
166	in → lb	Retail counter, economy tiers
250	in → lb	LTL freight density class
5000	cm → kg	International express
6000	cm → kg	Standard global parcel

Dimensional weight calculator

The formula

Divisor reference

Frequently asked questions

Why volumetric assessment matters