Class freight calculator - LTL freight class calculator by density

What is a class freight calculator?

A class freight calculator turns the physical measurements of a shipment into the freight class that less-than-truckload (LTL) carriers use to price it. You enter the length, width and height of one handling unit, the total weight and how many pieces you are shipping; the freight class calculator works out the total volume, divides the weight by that volume to get the density, and reads the resulting figure off the standard National Motor Freight Classification (NMFC) density table.

Freight class is a number from 50 to 500. Low numbers mean dense, compact, cheap-to-haul freight; high numbers mean light, bulky freight that fills a trailer without filling the weight limit. A pallet of bricks is class 50; a pallet of ping-pong balls is class 500.

Why freight class exists

A truck runs out of space long before it runs out of payload when it is loaded with light goods. If carriers charged by weight alone, a shipper sending 400 lb of packing foam that occupies half a trailer would pay the same as someone sending 400 lb of steel bar that occupies a single pallet position — and the carrier would lose money on the foam.

The NMFC, published by the National Motor Freight Traffic Association, solves this by sorting commodities into 18 classes. The classification balances four characteristics: density, stowability, ease of handling and liability. Density is the one you can measure yourself with a tape measure and a scale, and it is the characteristic that drives the class for the overwhelming majority of everyday shipments — which is why a density-based class freight calculator is the standard first estimate.

How does the calculator work?

The calculator runs three steps.

1. Total volume. Each dimension is converted to inches, multiplied together to get the cubic inches of one piece, divided by 1728 (the number of cubic inches in a cubic foot) and multiplied by the number of pieces.
2. Density. The total shipment weight, converted to pounds, is divided by the total volume in cubic feet.
3. Class. The density in lb/ft³ is matched against the 18 NMFC density bands.

You can type the dimensions in cm, m, in or ft and the weight in kg, metric tons, lb or US tons — the conversion happens before the arithmetic, so the class is the same whichever system you work in. The volume and density results have their own unit dropdowns, so you can read the volume in m³, L or ft³ and the density in kg/m³ or lb/ft³.

Measure the outside of the packaging, not the product. Pallet overhang, shrink wrap, crating and the pallet itself all take up trailer space, so they all count toward the volume that determines your class.

The formulas

Total volume in cubic feet, from the per-piece dimensions in inches and the piece count:

$V = \frac{L \times W \times H}{1728} \times n$

Density in pounds per cubic foot, from the total weight in pounds:

$D = \frac{M}{V}$

Here $L$, $W$ and $H$ are the length, width and height of a single piece in inches, $n$ is the number of pieces, $M$ is the total weight of the shipment in pounds, $V$ is the total volume in cubic feet and $D$ is the density in lb/ft³.

The NMFC density bands

The lower bound of each band is inclusive: a shipment at exactly 12.00 lb/ft³ is class 85, and one at 11.99 lb/ft³ drops to class 92.5.

Worked examples

Example 1 — a single standard pallet

A shipment of one pallet measuring 48 in long, 40 in wide and 48 in tall, weighing 600 lb in total.

Volume:

$V = \frac{48 \times 40 \times 48}{1728} \times 1 = 53.33 \text{ ft}^3$

Density:

$D = \frac{600}{53.33} = 11.25 \text{ lb/ft}^3$

11.25 lb/ft³ falls in the 10.5 to under 12 band, so the estimated freight class is 92.5.

Example 2 — four pieces

Four crates, each 40 in by 48 in by 45 in, weighing 1400 lb for the whole shipment.

Volume:

$V = \frac{40 \times 48 \times 45}{1728} \times 4 = 200 \text{ ft}^3$

Density:

$D = \frac{1400}{200} = 7 \text{ lb/ft}^3$

Exactly 7 lb/ft³ sits on the lower edge of the 7 to under 8 band, and lower bounds are inclusive, so the estimated freight class is 125.

Example 3 — metric entry

A one-cubic-metre crate: 100 cm by 100 cm by 100 cm, weighing 500 kg.

Converted, that is 35.31 ft³ and 1102.31 lb, giving:

$D = \frac{1102.31}{35.31} = 31.21 \text{ lb/ft}^3$

31.21 lb/ft³ falls in the 30 to under 35 band, so the estimated freight class is 60. Entering the same crate as 39.37 in by 39.37 in by 39.37 in at 1102.31 lb gives the identical answer — the units you type in do not change the class.

This is a density-based estimate, not the official NMFC class

The number this calculator returns is a density-based estimate. It is the right starting point for a quote and it matches the official class for most commodities, but it is not a substitute for looking up your NMFC item number.

The official classification assigned by the NMFTA weighs four characteristics, and density is only the first:

• Density — pounds per cubic foot, the calculation above.
• Stowability — how well the freight loads alongside other freight. Hazardous materials, oversized items, protruding shapes and goods that cannot be stacked are harder to stow and can be classed higher than their density suggests.
• Ease of handling — whether the shipment can be moved with ordinary equipment. Unusual shapes, fragile items and loads needing special care raise the class.
• Liability — the value per pound, and the risk of theft, damage or damaging neighbouring freight. High-value or perishable goods carry more liability and a higher class.

Some commodities also carry a fixed class in the NMFC regardless of how dense they happen to be, while others are density-based by definition and use exactly the table above. Certain items are further subject to a released-value rate that changes the class again.

Practical notes

• Round up your dimensions. Carriers measure to the outermost point and generally round each dimension up to the next whole inch. Measuring generously protects you from a reclassification.
• Reweigh, do not estimate. Carrier terminals run pallets over certified scales and forklift-mounted dimensioners. A guessed weight is the most common cause of a corrected invoice.
• A reclassification is expensive. If the carrier finds your density is lower than declared, they re-rate the shipment at the higher class and usually add an inspection fee, so an under-declared class rarely saves money.
• Density is per shipment, not per piece. A pallet of dense product and a pallet of light product moving on one bill of lading are averaged together, which is why the calculator asks for the total weight and the piece count rather than a per-piece weight.
• Watch the boundaries. Classes change on sharp edges, so a shipment sitting a fraction below a band boundary can often be moved into the cheaper class by using a slightly smaller box or consolidating two pieces into one. If you are near an edge, check the density calculator before you finalise the packaging.
• Keep the measurements on file. Recording the dimensions, weight and resulting density for each product you ship regularly makes future quotes fast and gives you evidence if a class is disputed.