Question 1

Why does a lower density mean a higher (more expensive) freight class?

Accepted Answer

LTL carriers price by how much trailer space a shipment occupies relative to its weight. A light, bulky shipment (low density) takes up space the carrier could otherwise fill with heavier freight, so it’s classified — and priced — as if it were more expensive to move, even though it weighs less.

Question 2

Is density the only factor in NMFC classification?

Accepted Answer

No — density is the default basis for many general commodities, but the National Motor Freight Classification also has specific item numbers for particular commodities that are classified regardless of density, based on additional factors like handling difficulty, stowability, and liability (risk of damage or theft). This calculator only estimates the density-based class.

Question 3

How should I measure an irregularly shaped shipment?

Accepted Answer

Use the smallest rectangular box that would fully contain the item — its maximum length, width, and height — even if the actual item doesn’t fill that whole box. Carriers dimension shipments this way because that’s the trailer space the shipment actually occupies.

Freight Shipping Class & Density Calculator

Density drives the class

Common questions