Freight Class Calculator (NMFC Density Method)
Enter your shipment's length, width, height and weight to find its NMFC freight class. The calculator computes volume, density in pounds per cubic foot, and maps the result to one of the 13 standard LTL freight classes (50 through 400) using the industry density table. Lower density means a higher class and higher carrier rates. Supports both inch/pound and centimeter/kilogram entries.
What is freight class and why does it matter?
Freight class is the NMFC (National Motor Freight Classification) number that carriers use to price less-than-truckload (LTL) shipments. There are 18 official classes ranging from 50 to 500, but for density-based commodities the 13-tier table from class 50 to class 400 covers the vast majority of everyday shipments. A lower class number means the freight is dense, easy to handle, and inexpensive to ship per pound. A higher class means the cargo is bulky, fragile, or hazardous, and costs more to move. Getting the class right protects you from carrier reclassification charges, which can add 30% or more to an invoice.
How to calculate freight class using density
The density method is the most common way to determine class for non-commodity-specific items. Step 1: measure length, width and height in inches. Step 2: multiply the three dimensions to get cubic inches, then divide by 1,728 to convert to cubic feet. Step 3: divide the total weight in pounds by the volume in cubic feet. The result is your density in PCF (pounds per cubic foot). Step 4: find where your PCF lands in the 13-tier NMFC table above. For metric shipments, convert centimeters to inches by dividing by 2.54 and kilograms to pounds by multiplying by 2.20462 before applying the same formula.
The four factors that determine NMFC class
Density is the primary factor for most commodities, but NMFC class is technically set by four characteristics: (1) Density - the weight-to-volume ratio, which drives cost efficiency for the carrier; (2) Stowability - how well the freight fits with other shipments in a trailer, items that are odd-shaped or hazardous score poorly; (3) Handling - fragile, perishable, or particularly heavy items require extra care and earn a higher class; (4) Liability - high-value goods or those prone to theft or damage carry a higher liability, pushing class up. The calculator uses density only, which is accurate for most general freight. Commodity-specific NMFC codes can override the density result, so always verify with your carrier for regulated or unusual items.
Tips for lowering your freight class
Because a lower class means lower rates, there are a few practical strategies shippers use. First, consolidate shipments: combining multiple pieces into one denser pallet increases PCF and can drop you one or two classes. Second, minimize void space in packaging by using appropriately sized boxes and reducing excess filler. Third, remove the pallet when weight allows - a standard 40 lb pallet adds volume without much density benefit on light shipments. Fourth, check whether your commodity has a specific NMFC item code that assigns a fixed class regardless of density - in some cases a code-based class is lower than what the density formula would suggest. Finally, weigh and measure accurately: carriers perform in-transit re-weigh and dimensioning, and corrections nearly always push the class and price up.
NMFC freight class density table
| Density (lb/ft3) | Freight class | Typical rate vs. class 100 | Description |
|---|---|---|---|
| 50 and above | 50 | ~35% of class 100 | Very dense - machinery, metal parts |
| 35 to <50 | 55 | ~45% of class 100 | Dense - bricks, cement, hardwood flooring |
| 30 to <35 | 60 | ~55% of class 100 | Dense - steel wire, auto parts |
| 22.5 to <30 | 65 | ~65% of class 100 | Moderate - bottled beverages, small motors |
| 15 to <22.5 | 70 | ~72% of class 100 | Moderate - car engines, food items |
| 12 to <15 | 85 | ~85% of class 100 | Average - crated machinery, cast iron stoves |
| 10 to <12 | 92.5 | ~92% of class 100 | Average - computers, sheet metal |
| 8 to <10 | 100 | 1.0x (baseline) | LTL benchmark - wine, furniture |
| 6 to <8 | 125 | ~125% of class 100 | Light - flat-screen TVs, small appliances |
| 4 to <6 | 175 | ~175% of class 100 | Light - clothing, auto parts in boxes |
| 2 to <4 | 250 | ~225% of class 100 | Very light - bamboo furniture, mattresses |
| 1 to <2 | 300 | ~300% of class 100 | Very light - wood cabinets, assembled furniture |
| Less than 1 | 400 | ~400% of class 100 | Extremely light - ping-pong balls, deer antlers |
Standard 13-tier density-to-class mapping used by most LTL carriers. Class 100 is the industry benchmark. Higher class numbers mean higher rates.
Frequently asked questions
What is the most common freight class?
Class 70 and class 100 handle the largest share of everyday LTL shipments. Class 100 is the industry benchmark and is considered the average for mixed freight. Many manufactured goods, food products, and consumer electronics fall between class 70 and class 125.
Can I ship class 50 freight?
Yes. Class 50 is the lowest and cheapest class, reserved for the densest freight - 50 lb/ft3 or above. Heavy machinery parts, copper wire, and steel products often qualify. You need a density of at least 50 pounds per cubic foot to reach class 50.
What happens if I use the wrong freight class?
Carriers weigh and measure shipments during transit. If your declared class is lower than what the density or commodity code warrants, the carrier will reclassify and bill you at the correct class plus a reclassification fee. These corrections can add 25-50% to the base freight charge, so accuracy pays.
Does density alone determine the final NMFC class?
Not always. Density is the starting point for most general freight, but many commodities have specific NMFC item codes that assign a fixed class or sub-class based on the type of product, packaging, and sometimes value per pound. For items like electronics, food, or hazardous materials, look up the NMFC item code in the NMFC directory or ask your carrier, because the code-based class can differ significantly from the density-based estimate.
How do I measure an irregularly shaped shipment?
Use the longest, widest, and tallest points of the shipment, including any protrusions, overhang, or asymmetric parts. The rule is to measure the smallest rectangular box that could fully contain the item. Carriers use automated dimensioners that capture the full outer envelope of the freight, so they will use the same bounding-box approach.
Should I include pallet weight and dimensions?
Yes, if the shipment is palletized. Include the pallet dimensions (typically 48 x 40 x 5.5 inches for a standard GMA pallet) and add the pallet weight (usually 35-45 lb) to the shipment weight. Carriers measure and weigh the pallet as part of the shipment. Forgetting the pallet usually understates the volume and overstates the density, which can result in a lower class estimate than the carrier will assign.