Calculating Volume: How to Calculate Cubic Meters

Ocean freight for clothing is bought by space as much as by weight: a container holds a fixed volume, and garments — light for their size — fill that volume long before they challenge its weight limit. That is why every apparel shipper needs to be able to turn a stack of cartons into a volume figure, in the cubic meters (CBM) that freight is commonly quoted and booked in.

The calculation itself is short and uses nothing more than a tape measure and three divisions. This guide walks through it exactly: measure one carton, convert its volume to cubic feet, convert cubic feet to cubic meters, then scale the result to the whole shipment. The companion pages on this site cover the weight side of the same shipment — calculating VGM and calculating volumetric weight.

Step 1: Measure One Carton

Start with a single carton of the shipment. Get the length x width x height for one carton — its three outside dimensions, measured the same way for every carton you calculate. Cartons of folded garments can bulge slightly when they are packed tight, so measure the carton as it will actually travel, not the flat box before packing.

Work in one unit throughout this step. If the dimensions are in inches, the multiplication gives cubic inches, which the next step converts. Mixing inches for one side and centimeters for another is the most common way this simple calculation goes wrong, so measure all three sides in the same unit before you multiply anything.

Step 2: Convert to Cubic Feet (CBF)

Take the length x width x height value for the carton and divide this value by 1,728. The result is the carton's volume in cubic feet, abbreviated CBF. The divisor is not arbitrary: one cubic foot contains 12 x 12 x 12 = 1,728 cubic inches, so dividing a volume measured in cubic inches by 1,728 restates it in cubic feet.

A worked example makes the arithmetic concrete. A carton measuring 24 inches long, 18 inches wide and 12 inches high has a volume of 24 x 18 x 12 = 5,184 cubic inches. Divided by 1,728, that is exactly 3 cubic feet — a 3 CBF carton. Every later step builds on this per-carton figure, so check it here before going on.

Step 3: Convert Cubic Feet to Cubic Meters (CBM)

Next, divide your CBF by 35.314. The result is the carton's volume in cubic meters — CBM, the unit in which container capacity and most ocean freight rates are expressed. The divisor is again a unit conversion: one cubic meter holds about 35.314 cubic feet, so dividing cubic feet by 35.314 restates the same volume in cubic meters.

Continuing the worked example: the 3 CBF carton divided by 35.314 gives about 0.085 CBM per carton. The figure looks small because a single apparel carton is a small fraction of a cubic meter — which is precisely why the next step, scaling the per-carton volume to the whole shipment, is where the commercially meaningful number appears.

Step 4: Scale to the Whole Shipment

Last, multiply the CBMs by the number of matching cartons. If the example shipment is 100 cartons of that same 24 x 18 x 12 size, its total volume is 0.085 x 100 = about 8.5 CBM. That total is the figure a freight forwarder uses to quote the shipment and to plan how much of a container it will occupy.

The multiplication step assumes matching cartons. When a shipment mixes sizes — a common pattern when several garment styles pack differently — run the first three steps separately for each carton size, multiply each size's CBM by its own carton count, and add the results. The total is the same kind of figure, built honestly from each size in the load. If the cartons travel on pallets, try the pallet load calculator to figure out how many cartons fit on the pallet, and calculate weight alongside volume: carriers compare the two, and the companion guides to calculating volumetric weight and calculating VGM (verified gross mass) cover the weight calculations a shipment needs.