Freight class is an NMFC rating from 50 to 500 based on density (pounds per cubic foot). Enter a shipment's weight and dimensions below and this calculator returns the class and PCF instantly, free, in your browser.
Class 70: typical for boxed food, tools and auto parts.
Get the class and density right before you book. Wrong class means a billing adjustment after delivery.
Carriers reclass and bill back when the freight class is wrong. A density-based calculation gives you the right starting class so your quote still holds when the carrier takes a second look.
The two tools on this site answer two different questions, and most shippers only need one of them on a given day. Reach for the Freight Class Calculator when you have a full set of dimensions and weight and just want the NMFC class plus a rough LTL cost range before you call a carrier or request a quote. Reach for the Density Calculator when you already know cubic feet, or when you are checking whether a packaging change moved a shipment across a density breakpoint. Both run the same density-to-class scale, so the class number will match either way. The difference is just which inputs you happen to have on hand at the dock.
A dispatcher confirming a single pallet before it leaves the warehouse usually wants the full calculator: weight, length, width, height, done. A planner comparing five packaging options against each other, or checking a spec sheet that already lists volume, tends to move faster with the density tool and a mental note of the class table above. Neither tool needs an account or a phone number. Numbers stay in the browser and nothing is saved once the tab closes.
If you ship the same commodity every week, run it through once, write down the class, and use the calculator again only when the packaging or the pallet size changes. Density only shifts when the box, the weight, or the wasted air space inside the box changes. A shipment that ships the same way twice will class the same way twice.
Both calculators run on one input: density, in pounds per cubic foot, mapped to the 18 NMFC class breakpoints from 50 to 500. That covers most general commodity freight correctly, because density is the primary factor the NMFC uses. It does not know about stowability, handling difficulty, or liability, the three other factors carriers and the NMFC manual weigh alongside density. It also cannot see a fixed NMFC item number. Thousands of specific commodities, hazmat included, carry an item number that locks in a class regardless of what the density math says. If your commodity has one, that number wins over this calculator's output every time.
The estimate assumes accurate measurements of the shipment as it will actually sit on the trailer, pallet and packaging included, rounded to the nearest inch on each side. Shave a few inches off the real footprint and the density comes out too high, which understates the class and understates the quote a carrier will eventually charge.
The most common mistake is measuring the box and forgetting the pallet. A 48 by 40 inch pallet under a shipment adds real height and footprint that carriers include and shippers sometimes do not. The second is estimating dimensions instead of measuring them. Rounding a shipment down because it looks close enough to a round number tends to bias the density estimate high and push the eventual carrier reclass the other way. The third is skipping the NMFC item number lookup for a commodity that ships often. If the same product moves every week, one call to a carrier or broker to confirm its item number saves repeated reclass surprises on every later shipment.
A fourth, quieter mistake is measuring loose freight instead of the shipment as it will actually travel. Boxes shift and settle in transit, and a carrier remeasures at the dock, not in your warehouse. If a shipment is banded, shrink-wrapped, or stacked on a pallet for the trip, measure it that way the first time, because that is the version the carrier will check against your paperwork. None of these mistakes are complicated to avoid. They just take an extra minute before the freight leaves the dock, which is cheaper than a billing adjustment that arrives after it already has.
One honest caveat: this calculator gives you a defensible starting number, not a binding rate. Carriers can still inspect, remeasure, and reclass a shipment at pickup or delivery. Use the class and cost range here to sanity-check a quote, not to skip the quote entirely.