Freight Class Calculator – Density and NMFC Class
Estimate the density and NMFC freight class of an LTL shipment. Enter dimensions and weight for up to 10 piece types, and get total volume, density in lb/ft³ and kg/m³, and the matching freight class.
Estimate Shipment Density and LTL Freight Class
Freight Class Formula
Where:
- \(V\) — volume of one piece in cubic feet (dimensions in inches divided by 1728, because \(1\ \text{ft}^3 = 1728\ \text{in}^3\))
- \(L\), \(W\), \(H\) — length, width and height of the piece (in)
- \(\rho\) — density in pounds per cubic foot (lb/ft³)
The total shipment volume is \(V \times Q\) for each piece type, summed over all types; total weight is the weight per piece multiplied by the quantity. The resulting density is then matched against the standard density guideline to estimate the NMFC freight class: the denser the shipment, the lower the class and the cheaper the rate per hundredweight tends to be.
Freight Class – Calculation Example
Example: a shipment of two pallets measuring 48 × 40 × 48 in at 500 lb each, plus one pallet of 48 × 40 × 40 in at 350 lb.
\[ V_1 = \frac{48 \times 40 \times 48}{1728} = 53.33\ \text{ft}^3, \quad 53.33 \times 2 = 106.67\ \text{ft}^3 \]
\[ V_2 = \frac{48 \times 40 \times 40}{1728} = 44.44\ \text{ft}^3 \]
\[ \rho = \frac{2 \times 500 + 350}{106.67 + 44.44} = \frac{1350}{151.11} = 8.93\ \text{lb/ft}^3 \]
Result: total volume 151.11 ft³, total weight 1,350 lb, density 8.93 lb/ft³ (≈ 143 kg/m³) — which falls in the 8–9 lb/ft³ range, so the estimated freight class is Class 110.
How to use the calculator
- Select the Number of pieces (piece types) in your shipment, from 1 to 10.
- Set Dimensions in to inches or centimeters and Weight in to pounds or kilograms — these units apply to every piece entered.
- For each piece type, enter its Length, Width and Height.
- Enter the Weight per piece and the Quantity — how many identical pieces share that exact size and weight.
- Read the results: Total volume (ft³), Total weight (lb), Density in lb/ft³ and kg/m³, and the Estimated freight class.
- Check the Piece breakdown table to verify each line and see the individual density of every piece type.
What is freight class and why does it matter?
In less-than-truckload (LTL) shipping, carriers price freight using the National Motor Freight Classification (NMFC), which groups commodities into 18 classes from 50 to 500. The class determines how much you pay per hundredweight (CWT), so an incorrect class means an incorrect quote — and when the carrier re-weighs and re-measures your shipment, the difference arrives as an unexpected adjustment on the invoice.
Density is the single biggest factor in classification. It is the ratio of the total weight to the total cubic feet of the shipment, including pallets, crating and packaging. Heavy, compact freight such as bricks or machinery is dense (often 30 lb/ft³ or more) and lands in low classes like 50 or 55. Light, bulky freight such as foam pillows or empty plastic containers can fall below 4 lb/ft³ and spikes into class 250 or worse, which can cost more per pound than the goods are worth.
To interpret the result: the lower the number, the higher the density and typically the lower the rate. A density of 8.93 lb/ft³ estimates class 110, but the exact class for a specific commodity is set by its NMFC item number, which may also consider stowability (how easily it fits with other freight), ease of handling, and liability (fragility, theft risk, perishability). The result therefore serves as a solid guideline and sanity check for quoting and budgeting, not a substitute for the official classification.
If your shipments involves odd sizes, you may also want to compute package footprints separately with the square footage calculator, or estimate lumber volumes with the board foot calculator before packing.
Density-to-class reference table
| Density (lb/ft³) | Freight class |
|---|---|
| 50 and above | 50 |
| 35 – 50 | 55 |
| 30 – 35 | 60 |
| 22.5 – 30 | 65 |
| 15 – 22.5 | 70 |
| 13.5 – 15 | 77.5 |
| 12 – 13.5 | 85 |
| 10.5 – 12 | 92.5 |
| 9 – 10.5 | 100 |
| 8 – 9 | 110 |
| 7 – 8 | 125 |
| 6 – 7 | 150 |
| 5 – 6 | 175 |
| 4 – 5 | 200 |
| 3 – 4 | 250 |
| 2 – 3 | 300 |
| 1 – 2 | 400 |
| Below 1 | 500 |
Assumptions and practical tips
- Rectangular pieces. The calculator assumes each piece is a rectangular box. For irregular shapes, use the smallest box that would enclose the piece — carriers measure to the extreme outer dimensions, including overhanging pallet wrap.
- Include packaging. Measure the pallet and packaging, not the bare product, and weigh everything together. A 40 lb pallet on a 150 lb load changes the density — and possibly the class.
- Metric inputs are converted. Centimeters and kilograms are converted internally to inches and pounds, the units the NMFC density guideline uses. The metric density shown is for reference.
- Density is a guideline, not the law. Many commodities are classified by their NMFC item number regardless of density; others have density sub-scales within one item. Always confirm the final class with your carrier or the official NMFC database before booking.
- Consolidate when possible. Mixing a heavy piece with a very light one averages the density upward, lowering the blended class — but the class applies to the whole shipment, so item-level quotes may still differ.
- Shippers who move goods in passenger vehicles may also find the luggage weight calculator or the trailer tongue weight calculator useful for weight-balancing loads.
Frequently Asked Questions
How do I calculate freight density by hand without a calculator?
Measure each piece to its extreme outer dimensions in inches, multiply length × width × height, then divide by 1,728 to get cubic feet (because one cubic foot is 1,728 cubic inches). Divide the total shipment weight in pounds by the total cubic feet. For example, a 48 × 40 × 45 in pallet at 400 lb is 53.33 ft³ (going by the longest points, including overhang), giving 400 ÷ 53.33 ≈ 7.5 lb/ft³.
What is a good density for LTL shipping?
Anything at or above roughly 10 lb/ft³ is considered decent and usually lands in class 92.5 or better, where rates are moderate. Densities of 15 lb/ft³ and up get into class 70 and below, which are among the cheapest. Below 6 lb/ft³ you enter class 150+, where light and bulky freight can cost more to move than the product is worth.
How do I convert between lb/ft³ and kg/m³?
Multiply lb/ft³ by 16.018 to get kg/m³, and divide kg/m³ by 16.018 to go back. So 8 lb/ft³ ≈ 128 kg/m³, and 200 kg/m³ ≈ 12.5 lb/ft³. Carriers in the US classify by lb/ft³, so even if you measure in centimeters and kilograms, the final quote is based on the imperial figure.
What is the difference between freight class and the NMFC item number?
The NMFC item number identifies your specific commodity and can even have density sub-scales within it, while the class (50–500) is the pricing category derived from it. Many items are classified purely by density, but others also factor in stowability, handling risk, and liability. Your estimate here is a solid guideline, but the carrier's official NMFC item number determines the final class.
Why did my carrier reclassify my shipment and charge more?
Carriers re-weigh and re-measure freight at their terminals, including pallets, packaging, and any overhanging pallet wrap. If your declared weight or dimensions were smaller than the actual freight, the density falls, the class rises, and the difference appears as a re-classification or re-weigh adjustment fee. Accurate outer-dimension measurement, including the pallet, is the best way to avoid surprise charges.
Should I measure the product or the pallet with its packaging?
Always measure and weigh the full packaged piece, pallet included, because that is exactly what the carrier does. A standard 48 × 40 in wood pallet typically weighs 35–50 lb, so ignoring it on a light load can push your real density down a class. Include skids, crates, shrink wrap, and any protruding handles or spouts in the dimensions.
How is freight class different from dimensional weight?
Dimensional weight applies mainly to parcel and air services and compares actual weight to a volumetric weight based on package size alone, typically divided by a divisor like 139. Freight class only exists in LTL ground shipping and prices shipments by density plus stowability, handling, and liability. Class does not use a dimensional weight formula at all, although density drives it in much the same way.