What is Freight Class 55? Density, Examples & Cost

Freight class 55 corresponds to a density of 35-50 pounds per cubic foot. Density is weight divided by volume, so a 1,700 lb shipment occupying 40 cubic feet has a density of 42.5 lbs/ft³ - squarely in the class 55 range. Compute your shipment's density with the Freight Class Calculator.

Class 55 is a very dense, economical class for heavy building and flooring materials. Commodities that commonly rate at this class include:

• Hardwood flooring
• Bagged cement and mortar
• Ceramic tile
• Moldings and millwork

These are typical examples - the binding class is always the commodity's actual NMFC provision, which you can confirm with the NMFC Lookup.

LTL carriers sell trailer space, so density drives price. Class 55 is cheaper than class 60 and more expensive than class 50. Because it sits on the dense end of the scale, class 55 earns the carrier good revenue per cubic foot, so the rate per hundredweight (CWT) is relatively low.

If your shipment is borderline between class 50 and class 60, packaging changes that adjust density can move it into an adjacent class and change the bill. A 1,700 lb shipment in 40 ft³ rates class 55 (42.5 lbs/ft³); spreading the same weight over more space lowers the density and bumps it toward class 60. Always confirm before quoting with the NMFC Lookup or the NMFC API.

Class 55's position on the freight class ladder, with its immediate neighbors:

• Class 50 (50+ lbs/ft³) - denser than class 55, so it rates a step cheaper. Typical freight: bricks, sand, and gravel.
• Class 55 (35-50 lbs/ft³) - a very dense, economical class for heavy building and flooring materials.
• Class 60 (30-35 lbs/ft³) - lighter than class 55, so it rates a step more expensive. Typical freight: car parts and accessories.

Because adjacent classes are separated by narrow density bands, an inch of extra packaging or a lighter-than-expected load can shift a shipment between them - so accurate measurement matters most near these boundaries. See Freight Class Explained for the complete 18-class ladder.

You can estimate class 55 yourself in three steps before you ever request a quote:

1. Measure the packaged shipment - length, width, and height in inches, including the pallet, crating, and any overhang.
2. Convert to cubic feet and divide: volume = (L × W × H) ÷ 1,728, then density = weight ÷ volume.
3. Match the density to the chart. A result of 35-50 pounds per cubic foot lands in class 55.

Note how sensitive the boundary is: a small change in volume moves the density out of the 35-50 band and into an adjacent class. The Freight Class Calculator runs this calculation automatically, and the NMFC API returns the authoritative class for a known commodity so your TMS never has to guess.

Most class 55 billing adjustments come from two avoidable mistakes:

• Measuring the product, not the packaged unit. Class is based on the shipment as tendered - pallet, crating, and overhang included. Measuring only the product understates volume and overstates density.
• Assuming density alone. Some commodities carry a fixed NMFC class regardless of density. Verify the item's actual provision instead of trusting the density estimate.

When a carrier inspects a shipment and finds the class understated, they reclassify it and rebill the difference, frequently adding an adjustment fee. For freight near class 55, the safest workflow is to measure precisely, calculate density, and then confirm the commodity's actual NMFC provision rather than trusting a single estimate. If the density comes back just above the range, the shipment may actually rate the cheaper class 50; if it comes back just below, expect the pricier class 60.

The procedure in How to Determine Freight Class walks through measuring, calculating density, and confirming the class so a carrier inspection doesn't surprise you. To classify at scale, the NMFC API returns the class and NMFC item number for any commodity in a single call - the same data, automated for your quoting or TMS pipeline.