If you’ve ever gotten a shipping quote that felt way higher than it should have been for a “small, light” package, cubic feet is probably the reason. Carriers don’t just price shipments on weight they price on the space a shipment takes up in a truck, container, or cargo hold. Knowing how to calculate cubic feet accurately is the difference between a fair freight rate and an expensive surprise on your invoice.
This guide walks through the exact formula, worked examples, how to convert to CBM for international shipments, and how cubic feet ties into dimensional weight and freight class.
What Is Cubic Feet and Why It Matters for Shipping
Cubic feet (ft³) is a unit of volume. It measures the amount of three-dimensional space a package, box, or pallet occupies. One cubic foot is a cube measuring 1 foot long, 1 foot wide, and 1 foot high.
For shippers, this number matters because carriers price freight and LTL (less-than-truckload) shipments using a combination of weight and volume, not weight alone. A shipment’s cubic footage directly affects how much you pay, how a container or trailer gets loaded, and how much warehouse space the item needs while it waits to ship.
Cubic feet is still the standard unit for domestic freight in the US and Canada. If you’re shipping internationally by ocean or air, you’ll more often see CBM (cubic meters) used instead we’ll cover how to convert between the two below. Cubic feet also feeds directly into density (weight divided by cubic feet), which is the number carriers use to assign an LTL shipment its freight class.
How to Calculate Cubic Feet Step by Step
Calculating cubic feet only takes three steps, and the same formula works whether you’re measuring a single box or a full pallet.
Step 1: Measure length, width, and height in inches. Always measure the outer dimensions of the packaging the box, crate, or pallet not just the product inside it. Packaging adds real volume that carriers will charge for.
Step 2: Multiply length × width × height. This gives you the volume in cubic inches.
Step 3: Divide by 1,728. There are 1,728 cubic inches in one cubic foot (12 × 12 × 12), so dividing your cubic inch total by 1,728 converts it to cubic feet.
Cubic Feet = (Length × Width × Height in inches) ÷ 1,728
Worked example: A pallet measures 48in x 40in x 48in. 48 × 40 × 48 = 92,160 cubic inches 92,160 ÷ 1,728 = 53.3 cubic feet
If your measurements are already in feet, you can skip the conversion entirely: Length (ft) × Width (ft) × Height (ft) gives you cubic feet directly.
Shipping more than one item? Calculate the cubic feet for each piece separately, then add the totals together to get the full shipment volume. Don’t just measure one box and multiply by quantity unless every piece is genuinely identical in size mixed pallets or cartons need to be measured individually for an accurate total.
Converting Cubic Feet to CBM (Cubic Meters)
If you’re quoting ocean freight, booking an international LCL (less-than-container-load) shipment, or working with a global freight forwarder, you’ll likely need CBM instead of cubic feet most international rate sheets are built around the metric system.
The metric version of the formula works the same way, just with different units and a different divisor:
CBM = (Length × Width × Height in cm) ÷ 1,000,000
To move between the two units, use these conversion factors:
- 1 cubic meter = 35.3147 cubic feet
- 1 cubic foot = 0.0283 cubic meters
Worked example: A carton measures 35cm x 35cm x 45cm. 35 × 35 × 45 = 55,125 cubic centimeters 55,125 ÷ 1,000,000 = 0.055 CBM
Canadian sellers moving goods internationally will run into CBM most often on ocean freight quotes and LCL bookings, so it’s worth keeping both formulas handy if you ship both domestically and abroad.
Cubic Feet, Dimensional Weight, and Freight Class
Once you know a shipment’s cubic feet, two related numbers come into play: dimensional weight and freight class.
Dimensional (DIM) weight is how carriers account for packages that are large but light. Rather than charging based on actual weight alone, they charge based on whichever is greater — the actual weight or the DIM weight. The parcel DIM weight formula is:
DIM Weight = (Length × Width × Height in inches) ÷ DIM divisor
The DIM divisor is typically 139 or 166, depending on the carrier and service level more on that below.
For LTL freight, the relevant concept is density, calculated as weight divided by cubic feet. Carriers use density to assign one of 18 NMFC freight classes, which in turn drives the per-pound rate you’re charged. Roughly speaking:
| Density (lbs/cu ft) | Approximate Freight Class |
|---|---|
| Under 1 | Class 400+ (highest cost) |
| 1–4 | Class 300–400 |
| 4–8 | Class 150–250 |
| 8–12 | Class 100–125 |
| 12–20 | Class 70–92.5 |
| Over 20 | Class 50–65 (lowest cost) |
In general, lower-density shipments (bulky and light) get a higher, more expensive freight class, while denser, more compact shipments get a lower, cheaper class.
One important caveat: Canada Post, Purolator, FedEx, and UPS each publish their own DIM divisor, and these figures do change from time to time. Always confirm the current divisor with your carrier before quoting a rate, rather than assuming it matches a previous shipment.
How to Calculate Freight Class From Cubic Feet
If you’re shipping LTL freight, here’s how to go from a raw measurement to an estimated freight class:
Step 1: Calculate the shipment’s total cubic feet using the formula above.
Step 2: Divide the shipment’s weight in pounds by its cubic feet to get density in pounds per cubic foot (PCF).
Step 3: Match that PCF figure to the NMFC freight class table. Lower density (bulky, lightweight) shipments land in a higher, more expensive class; denser, more compact shipments land in a lower, cheaper class.
Worked example: A 500 lb shipment measures 16 cubic feet. 500 ÷ 16 = 31.3 PCF, which places it in a mid-range freight class.
Getting this calculation right upfront matters more than it might seem. Misclassifying freight class is one of the most common reasons carriers issue LTL rate reclassification fees after pickup an accurate cubic feet measurement at the time of booking is the easiest way to avoid a surprise invoice adjustment later.
Common Mistakes When Calculating Cubic Feet
A few small errors show up again and again in cubic feet calculations, and each one can throw off your shipping cost estimate:
- Forgetting to multiply by quantity when shipping multiple identical pieces, understating total volume
- Mixing units measuring one side in inches and another in centimeters or feet
- Measuring the item instead of the outer packaging, which understates the true shippable volume
- Using the wrong DIM divisor for the carrier or service level, leading to inaccurate rate estimates
- Rounding too early in multi-step calculations, which compounds small errors across a multi-pallet shipment
Double-checking units and measuring the full packaged item every time avoids most of these issues.
FAQ
How do I calculate cubic feet for a pallet? Multiply the pallet’s length, width, and height in inches, then divide by 1,728. A standard 48 x 40 x 48-inch pallet works out to 48 × 40 × 48 = 92,160 cubic inches, and 92,160 ÷ 1,728 = 53.3 cubic feet. Always measure the loaded pallet, including any overhang from the goods, not just the pallet base.
What is the formula for cubic feet? The standard formula is Cubic Feet = (Length × Width × Height in inches) ÷ 1,728. If your measurements are already in feet, you can skip the division and simply multiply Length (ft) × Width (ft) × Height (ft) directly to get cubic feet.
How do I convert cubic inches to cubic feet? Divide the total cubic inches by 1,728, the number of cubic inches in one cubic foot (12 × 12 × 12). For example, 3,456 cubic inches divided by 1,728 equals exactly 2 cubic feet.
Do I measure in inches or feet for cubic feet calculations? Either works as long as you’re consistent across all three dimensions. Most shippers measure in inches for accuracy on smaller packages, then divide by 1,728 to convert. For large freight or storage space, measuring directly in feet and multiplying is often faster.
What is the difference between CBM and cubic feet? Cubic feet (ft³) is the imperial unit of volume used mainly in US and Canadian domestic freight, while CBM (cubic meters, m³) is the metric unit used in most international ocean and air freight pricing. One cubic meter equals approximately 35.3 cubic feet, so converting between the two is straightforward with that factor.
How does cubic feet affect shipping cost? Carriers price many shipments on dimensional or volumetric weight rather than actual weight alone, especially for large, lightweight items. A higher cubic feet figure relative to actual weight can push a shipment into a higher price bracket or a less favorable LTL freight class, even if the package itself is light.
What is a good freight density for LTL shipping? Generally, a density above roughly 12 pounds per cubic foot qualifies for a lower, less expensive freight class, while lighter, bulkier shipments below that threshold get classed higher and cost more per pound to ship. Calculating cubic feet accurately is the first step to knowing where your shipment falls.
Cathy is a Business Development Executive at ShippingChimp. I work closely with D2C brands, founders, and operations teams to reduce shipping costs, improve fulfillment efficiency, and strengthen unit economics, without disrupting their existing tech stack.
