Logistics Guide
How to Calculate Freight Class: A Step-by-Step Guide
Misclassifying LTL freight is one of the most common — and most expensive — mistakes in shipping. This guide walks you through the density formula, the full NMFC freight class table, and how chargeable weight differs from freight class so you can quote shipments accurately the first time.
What is freight class?
Freight class is a standardized category defined by the National Motor Freight Classification (NMFC). LTL (Less-Than-Truckload) carriers use it to price shipments consistently. There are 18 classes ranging from 50 (densest, cheapest) to 500 (lightest, most expensive). Class is driven primarily by density, but stowability, handling, and liability also factor in.
The 5-step calculation
Step 1 — Measure
Length × Width × Height in inches at the widest points, including pallet and packaging.
Step 2 — Cubic feet
Multiply L × W × H, then divide by 1,728 to convert cubic inches to cubic feet.
Step 3 — Density
Density = Total Weight (lbs) ÷ Cubic Feet. This single number drives most of your class lookup.
Step 4 — Match the class
Use the NMFC density scale below to find the matching class from 50 to 500.
Step 5 — Compare to chargeable weight. For air, courier, and parcel shipments, calculate dimensional weight (L × W × H ÷ a DIM divisor like 139 or 166) and use the higher of actual vs dimensional as the chargeable weight. LTL freight uses class; air and parcel use chargeable weight — both protect carriers from low-density cargo eating space they can't sell.
Worked example
A pallet measures 48" × 40" × 48" and weighs 600 lbs.
- Volume: 48 × 40 × 48 = 92,160 in³ → 92,160 ÷ 1,728 = 53.33 ft³
- Density: 600 ÷ 53.33 = 11.25 lbs/ft³
- Lookup: 9–12 lbs/ft³ → Class 100
NMFC freight class table
| Class | Density (lbs/ft³) | Example commodities |
|---|---|---|
| 50 | Over 50 lbs/ft³ | Bricks, steel parts |
| 55 | 35–50 | Hardwood flooring |
| 60 | 30–35 | Car accessories, glass |
| 65 | 22.5–30 | Books, bottled beverages |
| 70 | 15–22.5 | Auto engines, food items |
| 85 | 12–15 | Crated machinery |
| 100 | 9–12 | Boat covers, canvas |
| 125 | 7–9 | Small appliances |
| 150 | 6–7 | Auto sheet metal |
| 175 | 5–6 | Clothing, couches |
| 200 | 4–5 | Aircraft parts, mattresses |
| 250 | 3–4 | Bamboo furniture, plasma TVs |
| 300 | 2–3 | Wood cabinets, tables |
| 400 | 1–2 | Deer antlers |
| 500 | Under 1 | Ping pong balls, gold dust |
Freight class vs chargeable weight
| Aspect | Freight Class (LTL) | Chargeable Weight (Air/Parcel) |
|---|---|---|
| Used by | LTL trucking carriers | Air freight, couriers, parcel |
| Driven by | Density + stowability, handling, liability | Higher of actual vs dimensional weight |
| Formula | Weight ÷ Cubic Feet → NMFC class | (L × W × H) ÷ DIM divisor (139 / 166 / 6000) |
| Output | Class 50–500 | Weight in lbs or kg |
| Penalty for errors | Reclassification fee + corrected invoice | Reweigh surcharge on next invoice |
How to avoid reclassification fees
- Measure to the widest point — overhang counts.
- Include pallet, dunnage, shrink wrap, and packaging in both weight and dimensions.
- Round dimensions up to the next whole inch before calculating.
- Re-check density any time the SKU, packaging, or pallet pattern changes.
- Keep a record of the NMFC item number you declared, not just the class.
Calculate it instantly
Skip the spreadsheet. Use the LogiDesks freight calculators to compute CBM, volumetric weight, and chargeable weight in seconds — and save every quote to history.
FAQs
What is freight class?
Freight class is a standardized NMFC code (50–500) that LTL carriers use to price shipments. It is based on density, stowability, handling, and liability.
How do I calculate freight class?
Calculate density (weight ÷ cubic feet), then look up the matching class on the NMFC density scale. Lower density usually means a higher class and higher cost.
What is the difference between freight class and chargeable weight?
Freight class is the NMFC category used for LTL pricing. Chargeable weight is the higher of actual weight and dimensional (volumetric) weight used by air and parcel carriers.
What happens if I declare the wrong freight class?
Carriers reweigh and re-measure shipments. An incorrect class triggers a reclassification fee and a corrected invoice, often days after delivery.