LTL carriers price freight by its NMFC class, and the class hinges first on density — how many pounds you pack into each cubic foot. This calculator works out your shipment’s density, maps it to the standard class scale, then adjusts for the three non-density factors that can push a commodity into a higher class.
How it works
Freight class is set by four factors. Density is computed directly:
volume (ft³) = length × width × height / 1728 (inches)
density PCF = weight (lb) / volume (ft³)The PCF value is matched against the standard density table: 50 PCF or more is class 50, around 5.6 PCF is class 150, and under 1 PCF is class 400 or 500. Lower density means a higher class. The other three factors then adjust it:
- Stowability — odd shapes, hazmat, or items that cannot be stacked or placed alongside standard freight classify higher.
- Handling — fragile or special-care freight that requires extra labour classifies higher.
- Liability — high-value, perishable, or theft-prone goods classify higher.
Each adverse factor bumps the class up one or more steps on the class scale.
The standard freight class density table
| Density (PCF) | Freight class |
|---|---|
| 50+ | 50 |
| 35–50 | 55 |
| 22.5–35 | 60 |
| 15–22.5 | 65 |
| 13.5–15 | 70 |
| 12–13.5 | 77.5 |
| 10.5–12 | 85 |
| 9–10.5 | 92.5 |
| 8–9 | 100 |
| 7–8 | 110 |
| 6–7 | 125 |
| 5–6 | 150 |
| 4–5 | 175 |
| 3–4 | 200 |
| 2–3 | 250 |
| 1–2 | 300 |
| Under 1 | 400 |
| Very light or hard to handle | 500 |
Class 50 is the cheapest to ship per pound; class 500 is the most expensive.
Worked examples
Standard pallet of packaged goods:
Dimensions 48 × 40 × 48 inches. Volume: 48 × 40 × 48 / 1728 = 53.3 ft³. Weight: 300 lb. Density: 300 / 53.3 = 5.63 PCF → class 150.
Dense steel parts on a half-pallet:
Dimensions 48 × 40 × 24 inches. Volume: 48 × 40 × 24 / 1728 = 26.7 ft³. Weight: 800 lb. Density: 800 / 26.7 = 30 PCF → class 60. Much cheaper per pound because the load is dense.
Light foam packaging:
Dimensions 48 × 40 × 48 inches. Weight: 50 lb. Density: 50 / 53.3 = 0.94 PCF → class 400. Expensive because it occupies lots of trailer space per pound of freight.
How to reduce your freight class (and your bill)
The density-class relationship gives shippers a direct lever: pack denser. Practical ways to improve density:
- Remove excess packaging. Oversized boxes filled with air inflate your volume calculation without adding useful weight.
- Combine small shipments. Aggregating multiple small orders into one larger pallet often achieves a higher density.
- Use shrink-wrap or banding to consolidate items onto a pallet rather than shipping loose or in oversized crates.
- Check whether your commodity has a fixed NMFC item number. Some products (electronics, auto parts, chemicals) have a published class that overrides the density calculation. If your commodity’s fixed class is lower than the density-based class, use it.
When to verify against the official NMFC book
This tool estimates class from density and the four qualitative factors. Some commodities have a fixed NMFC item number — an assigned class published in the National Motor Freight Classification directory that supersedes density entirely. Examples include fragile art glass (always class 400 regardless of density) and certain chemicals with mandatory high liability ratings. If you are unsure whether your commodity has a fixed class, contact your freight broker or the NMFTA (National Motor Freight Traffic Association) to look it up. Using the wrong class can lead to carrier reclassification charges and unexpected invoice adjustments.