Dimensional weight overcharges: how to spot billing errors

By Meet Bhadani, Maritime Freight Review, Moncton, NB. Updated 26 October 2026.

Carriers do not always bill you for what a shipment weighs. If a package is large and light, they can bill for the space it takes up instead. This is called dimensional weight, and mistakes in how it is applied are a common source of overcharges.

How dimensional weight works

The carrier calculates a dimensional weight from the package size, then bills the greater of the actual weight and the dimensional weight.

Dimensional weight = (length × width × height) ÷ divisor

The divisor is set by the carrier or in your agreement. Figures such as 139 and 166 are common in inches and pounds, and 5,000 is common in centimetres and kilograms, but your agreement is what counts. A smaller divisor means a higher billed weight.

Illustrative example (made-up shipment). A box measures 24 × 18 × 12 inches and weighs 20 lb. Volume: 24 × 18 × 12 = 5,184 cubic inches. With a divisor of 139: 5,184 ÷ 139 ≈ 37.3, rounded up to 38 lb billed. With a divisor of 166: 5,184 ÷ 166 ≈ 31.2, rounded up to 32 lb billed. If your agreement says 166 and you were billed on 139, you paid for 6 extra pounds on that shipment.

Where dimensional weight errors happen

Wrong divisor. The carrier uses a divisor that differs from your agreement.
Wrong measurements. The carrier recorded larger dimensions than the real package, for example by measuring a bulge or packaging.
Extra rounding. Each dimension is rounded up before multiplying, which inflates the result.
Not allowed by your agreement. Dimensional weight is applied to shipments or services where your agreement says actual weight applies.
Wrong rate for the weight. The weight is right, but the wrong price bracket is used.
Duplicate fees. A reweigh or remeasure fee is charged on top of the weight change.

How to check it

Find the weight and dimensions the carrier billed on the invoice.
Compare them with your own records: shipping log, bill of lading, packing list, photos.
Find the divisor in your rate agreement and redo the calculation.
Check which rate bracket applies to the correct weight.
Compare with the amount billed.

An important limit

Carriers usually treat their own scale and measurements as correct unless you show otherwise. A wrong divisor or arithmetic error can be proven from the invoice and your agreement. A claim that the carrier measured the box wrongly needs your own evidence, such as weights, photos or a signed bill of lading. Keep these records when you ship.

Common questions

What is dimensional weight?

It is a weight the carrier calculates from the package size. The carrier bills the greater of the actual weight and the dimensional weight.

Can a carrier change the weight or size I entered?

Yes, carriers often remeasure shipments and adjust the bill. You can dispute it, but you will need your own evidence, such as weights, photos or a bill of lading.

Where do I find my dimensional weight divisor?

In your rate agreement or the carrier's published service terms. If it is not stated, ask your carrier to confirm it in writing.

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