Freight Class Calculator

What's a Freight Class?

When you ship products via LTL (Less-Than-Truckload), your shipment gets assigned a freight class, a standardized code between 50 and 400 that carriers use to determine your shipping rate. Carriers use this code to price shipments based on what you're sending and how it handles in transit.

In July 2025, the NMFTA streamlined this into a 13-tier density-based scale (down from 18 classes). Class 50 covers the densest, easiest-to-handle freight and carries the lowest rates. Class 400 covers the lightest, bulkiest items and carries the highest. Knowing where your shipment falls helps you budget accurately and avoid reclassification fees.

The classification system was created by the National Motor Freight Traffic Association (NMFTA) and is used by virtually every LTL carrier in North America. Whether you're shipping a pallet (skid) of canned goods or a crate of electronics, your freight class directly impacts what you pay.

How to Calculate Your Freight Class

Freight class is primarily based on density: the relationship between your shipment's weight and the space it occupies. Here's how to calculate it in three steps:

Once you have your density in pounds per cubic foot, match it to a freight class using the reference chart above, or enter your dimensions and weight into the calculator to get your result instantly.

Measurement tips

Always measure the outer dimensions of your packaging, not the product inside. Carriers measure the footprint your shipment occupies on the truck, so it's the box that counts. For palletized freight, measure the full pallet including any overhang.

What Determines Your Freight Class?

While density is the most common factor (and what our calculator uses), carriers may evaluate four characteristics when classifying your shipment.

Density

The weight per cubic foot of your shipment. This is the primary factor for most freight and the basis for density-based classification. Heavier, more compact shipments qualify for a lower class and a lower rate.

Stowability

How easily your freight can be arranged alongside other shipments on the truck. Standard pallets stow easily. Irregular shapes, oversized items, or hazardous goods are harder to stow and may result in a higher class.

Handling

Whether your shipment requires special equipment or attention during loading and transport. Freight that needs extra handling (fragile goods, temperature-sensitive products) may be classified higher.

Liability

The risk associated with shipping your goods, including their value, fragility, and susceptibility to damage or theft. Higher-value or more perishable items carry more liability for the carrier.

For most standard shipments, density alone determines the class. However, certain commodities like hazardous materials, fine art, or live plants may be assigned a fixed class regardless of their density.

Freight Classes for Corrugated Packaging

Corrugated packaging has specific NMFC (National Motor Freight Classification) codes that determine how carriers classify it for LTL shipping. If you're shipping pallets of boxes — whether flat-packed or assembled — knowing the right code helps you avoid reclassification fees and quote accurately.

Common NMFC codes for corrugated products

Three NMFC codes cover the majority of corrugated packaging shipments:

• NMFC 29785 — most flat corrugated mailer boxes, the most common code for e-commerce packaging
• NMFC 29800 — corrugated containers and shipping boxes (general category)
• NMFC 29810 — corrugated partitions and dividers

How flute type affects weight and density

The flute profile of your corrugated board directly impacts the weight and density of your shipment, which in turn affects your freight class:

• E-flute (1/16") — lightest, used in mailer boxes and retail packaging
• B-flute (1/8") — good balance of cushioning and printability, common in mailer boxes
• C-flute (5/32") — standard shipping box flute, more cushioning
• BC double wall — heaviest, used for heavy or fragile goods

The specific NMFC sub-code depends on construction (single wall vs double wall), whether the box is shipped knocked flat or assembled, and the commodity packed inside. Always verify the specific NMFC code with your carrier or freight broker before shipping.

For most Packwire customers shipping custom mailer boxes or custom shipping boxes, NMFC 29785 or 29800 will apply.

Worked Example

Let's say you're shipping a pallet (sometimes called a skid) of packaged goods. The shipment measures 48" × 40" × 36" and weighs 275 lbs. Here's how to find the freight class:

At Class 125, this shipment falls in the mid-range, common for items like small appliances and vending machines. If you could reduce the box size or add more weight to the pallet, you might push the density above 8 and qualify for Class 100, which would mean a lower shipping rate.

How right-sizing helps

Now imagine you swap that oversized 48" × 40" × 36" box for a custom box that fits snugly at 40" × 30" × 24", same 275 lbs:

By right-sizing the packaging, this shipment drops from Class 125 to Class 70, a meaningful reduction in per-shipment cost from eliminating wasted cube. For recurring shipments, the savings compound quickly. Use our Box Size Optimizer to find the ideal dimensions for your products.

Tips for Reducing Your Shipping Costs

Your freight class directly impacts your bottom line. Here are a few practical ways to optimize your shipments and potentially qualify for a lower class.

Right-size your packaging

Use the smallest box or crate that safely fits your product. Eliminating void space increases density, which can move you into a lower freight class. This is one of the most straightforward optimizations, and it's what custom packaging is designed for. Packwire offers custom shipping boxes and custom mailer boxes built to exact dimensions, so every shipment is as dense as possible. Even trimming a couple of inches off each dimension can meaningfully change your density calculation and bump you into a lower class.

Palletize efficiently

Stack cartons to maximize pallet cube utilization. A tightly packed, shrink-wrapped pallet will yield a noticeably better density than loosely stacked boxes. When possible, arrange cartons so they interlock and fill the full pallet footprint — a standard 48" × 40" pallet with gaps around the edges wastes cube that you're paying for. If your boxes don't tile neatly onto the pallet, consider adjusting your box dimensions so they do.

Consolidate smaller shipments

Rather than sending multiple small packages individually, combine them onto a single pallet. More weight on the same footprint means better density, and LTL carriers charge per shipment, so fewer shipments also means fewer accessorial fees, fuel surcharges, and handling charges. If you ship to the same destination regularly, consolidating into weekly pallets instead of daily parcels can add up to significant savings.

Measure accurately

Carriers will re-weigh and re-measure at the terminal. If your actual dimensions don't match what you declared, expect reclassification fees and adjusted invoices. Use a tape measure on the outer dimensions of the packed box (not the product inside), and weigh on a calibrated scale. Rounding down or estimating may save a few minutes upfront but can cost you in surprise charges later.

Compare quotes from multiple carriers

Different LTL carriers price the same freight class differently depending on the lane, volume discounts, and their own network capacity. It pays to compare rates from at least two or three carriers, especially on recurring lanes where even a small per-shipment difference compounds over time. Many third-party logistics platforms let you compare quotes side by side in minutes.