How to Calculate Freight Class (NMFC Guide for Shippers)
Freight class determines a big chunk of your LTL rate. Here's how the NMFC system works, how to calculate density, and how to avoid costly reclassification fees.
You can do everything else right — compare LTL carriers, negotiate a solid rate, book the shipment on time — and still end up with an invoice $200 higher than your quote. The most common reason? Freight class.
Carriers reweigh and inspect LTL shipments at their terminals. If your freight class doesn't match what they find, they'll reclassify it, reprice the shipment, and send you an adjusted invoice — often with a fee added on top. It's one of the most frustrating parts of LTL shipping, and it's almost entirely avoidable with the right information upfront.
Here's how freight class works and how to calculate it correctly before you book.
The NMFC system, briefly explained
The National Motor Freight Classification (NMFC) is a standardized pricing system developed by the NMFTA (National Motor Freight Traffic Association). It assigns every type of commodity a class number between 50 and 500 based on four factors: density, stowability, handling difficulty, and liability.
The general rule: lower class = denser, easier freight = lower rate. Class 50 (the lowest) covers dense commodities like bricks, sand, and hardwood flooring. Class 500 (the highest) covers things like ping-pong balls — extremely light and bulky relative to their value.
Most common manufactured goods fall somewhere in the middle, between Class 85 and Class 150.
The four factors that determine class
Density is the most important factor for most commodities, and it's the one shippers most often get wrong. More on this below.
Stowability refers to how easily your freight can be loaded alongside other shipments. Oddly shaped items, hazardous materials, or freight that can't be stacked alongside other cargo gets a higher class.
Handling accounts for how difficult your freight is to load and move. Fragile items, freight that requires special equipment, or cargo that's prone to damage in transit all carry higher classifications.
Liability reflects the carrier's exposure if your freight is lost or damaged. High-value or theft-prone commodities carry a higher class to account for that risk.
How to calculate freight class by density
For most commodities — especially manufactured goods, industrial products, and consumer goods — class is determined by density. Here's the step-by-step calculation:
Step 1: Measure your shipment. Measure length, width, and height in inches after packaging. Include the pallet. A common mistake is measuring the product without the pallet or packaging — the carrier measures the whole thing. If you're not sure how to build the pallet correctly in the first place, see our guide on how to ship a pallet.
Step 2: Calculate cubic feet. Multiply length × width × height, then divide by 1,728 (the number of cubic inches in a cubic foot).
Example: A pallet measuring 48" × 40" × 52" 48 × 40 × 52 = 99,840 ÷ 1,728 = 57.8 cubic feet
Step 3: Calculate PCF (pounds per cubic foot). Divide your total weight — again, including the pallet — by cubic feet.
Example: 600 lbs ÷ 57.8 = 10.4 PCF
Step 4: Find your class.
| Density (PCF) | Freight Class |
|---|---|
| 50 or more | Class 50 |
| 35–50 | Class 55 |
| 30–35 | Class 60 |
| 22.5–30 | Class 65 |
| 15–22.5 | Class 70 |
| 13.5–15 | Class 77.5 |
| 12–13.5 | Class 85 |
| 10.5–12 | Class 92.5 |
| 9–10.5 | Class 100 |
| 8–9 | Class 110 |
| 7–8 | Class 125 |
| 6–7 | Class 150 |
| 5–6 | Class 175 |
| 4–5 | Class 200 |
| 3–4 | Class 250 |
| 2–3 | Class 300 |
| 1–2 | Class 400 |
| Less than 1 | Class 500 |
At 10.4 PCF, the example shipment falls into Class 100.
When density isn't the whole story: NMFC item numbers
Some commodities have a specific NMFC item number that assigns a fixed class regardless of what the density calculation says. Furniture, electronics, automotive parts, and dozens of other product categories fall into this bucket.
If your commodity has an NMFC item number, that classification takes precedence over density. You can look these up at nmfta.org, or — easier — ask your freight broker to verify before you quote. We do this on every LTL shipment we handle.
What happens when freight gets reclassified
A carrier inspector at a terminal can pull any LTL shipment for inspection. If they believe the freight class is wrong, they'll re-measure, reweigh, and reclassify. The result is an invoice correction — your new, higher rate — plus a reclassification fee that varies by carrier.
There's not much you can do after the fact. Your best defense is accuracy before the shipment moves.
The most common causes of reclassification:
- Measuring without the pallet (adds cubic feet and lowers density)
- Rounding down on dimensions
- Using an NMFC item number that doesn't match the actual commodity
- Assuming a class based on a similar shipment without verifying
Working with a freight broker to get class right
At Route 89, we check freight class on every LTL quote we run. If something doesn't look right — if your density calculation puts you at Class 85 but your product has a fixed NMFC item number at Class 125 — we'll catch it before the shipment moves.
That way, the rate you see on your LTL shipping quote is the rate you pay. No corrections, no surprises.
Request a quote today and we'll handle the classification for you.