Freight Class Calculator
Determine the NMFC freight class of a less-than-truckload (LTL) shipment using its dimensions, weight, and commodity type. Use this before booking LTL freight to avoid reclassification fees at the dock.
About this calculator
Freight class is an 18-tier NMFC system (from Class 50 to Class 500) that standardizes LTL pricing. The primary driver is density, measured in pounds per cubic foot (PCF): Density = weight / (length × width × height / 1728), where dividing by 1,728 converts cubic inches to cubic feet. Once density is known, it maps to a class: density < 1 PCF → Class 400; 1–2 PCF → Class 300; 2–4 PCF → Class 250; 4–6 PCF → Class 175; 6–8 PCF → Class 125; 8–10 PCF → Class 92.5; ≥ 10 PCF → Class 85. A commodityType multiplier then adjusts the output for goods with special handling, liability, or stowability characteristics defined by the NMFC. Higher classes cost significantly more to ship per hundredweight (CWT).
How to use
Imagine you're shipping a 200 lb pallet of boxed electronics measuring 48 × 40 × 36 inches, with a commodityType multiplier of 1.0. Step 1 — calculate volume in cubic feet: (48 × 40 × 36) / 1728 = 69,120 / 1,728 = 40 cu ft. Step 2 — calculate density: 200 / 40 = 5 PCF. Step 3 — map to class: 5 PCF falls in the 4–6 range → Class 175. Step 4 — apply commodity multiplier: 175 × 1.0 = Class 175. Your shipment should be quoted as Freight Class 175.
Frequently asked questions
How is freight class density calculated for an LTL shipment?
Density is calculated by dividing the shipment's weight in pounds by its volume in cubic feet. Since most measurements are taken in inches, the volume in cubic inches (length × width × height) must be divided by 1,728 to convert to cubic feet. For example, a 100 lb box that measures 24 × 24 × 24 inches has a volume of 8 cubic feet and a density of 12.5 PCF, placing it in Class 85. Accurate measurements are critical — carriers re-measure at the dock, and a mismeasured shipment can be reclassified, resulting in unexpected charges.
What happens if I declare the wrong freight class when booking LTL shipping?
If you under-declare your freight class, the carrier will issue a freight bill correction — sometimes called a 'reweigh and reclassification' notice — charging you the difference plus an administrative fee. These corrections can arrive days or weeks after delivery, making them difficult to budget for. Carriers use calibrated scales and laser dimensioners to verify density and class at origin or destination terminals. Using this calculator before booking helps you declare the correct class upfront, avoiding disputes and surprise invoices.
Why does commodity type affect freight class beyond just density?
The NMFC considers four factors when assigning freight class: density, stowability, handling difficulty, and liability (value and damage susceptibility). Commodity type captures these non-density factors. Fragile items, hazardous materials, or unusually shaped goods may be assigned a higher class than their density alone would suggest. For instance, a low-density commodity like furniture may carry a higher class multiplier due to its susceptibility to damage and awkward stowability. Always verify your commodity's NMFC item number with your broker or carrier to confirm the correct class.