Two unit systems, one shipment
The awkward part of measuring freight in Canada is rarely the arithmetic. It is that the packing list arrived in centimetres, the carrier quotes in cubic feet, and somebody has to reconcile the two without introducing an error along the way.
This page takes the unit on each line separately. A skid measured in inches, cartons measured in centimetres and a crate measured in feet can all sit in the same consignment; each is converted on its own before anything is summed, and both totals — cubic metres and cubic feet — come out together.
Lines are added, never averaged. An averaged unit standing in for several real sizes is a different calculation with a different answer, not a close approximation, and on a mixed skid load the gap is easily a cubic metre.
Internally every measurement is an exact fraction rather than a decimal, so 40 × 30 × 25 cm × 10 reads as exactly 0.3 m³ instead of the 0.30000000000000004 ordinary machine arithmetic produces for that particular product.
Converting between cubic metres and cubic feet
One cubic metre is 35.3147 cubic feet and one cubic foot is 0.0283 cubic metres. Both figures come from a definition rather than a measurement: the international foot is exactly 0.3048 m, so a cubic foot is exactly 0.028316846592 m³. That exactness is why a value converted and converted back comes out unchanged here instead of drifting.
The inch works the same way — exactly 2.54 cm, so a cubic inch is exactly 0.000016387064 m³. If you prefer the divisor form, multiply the three inch measurements and divide by 61,023.744.
A 48 × 40 × 48 inch skid, the common North American footprint loaded to four feet, is 92,160 cubic inches. That is 1.5102 m³, or 53.33 cubic feet.
The conversion block above the article moves between cubic metres, cubic feet and litres directly when you already have a figure and only need it in another unit.
The formula, and a mixed-unit example
In metres the formula holds nothing back: CBM = length × width × height × quantity.
Take a consignment with both unit systems in it. Two skids at 48 × 40 × 48 inches are 1.5102 m³ each, so 3.0205 m³. Ten cartons at 40 × 30 × 25 cm are 0.03 m³ each, so 0.30 m³. The shipment comes to 3.3205 m³, which is 117.2611 cubic feet.
Convert by hand instead and the usual slip is rounding the inch-to-metre step to 0.025 before cubing it — which looks harmless and lands 4.65 % low on the skid volume. The unit selector avoids the question entirely.
Quantity is a plain multiplier, so doubling a line doubles its volume and nothing else moves. That gives you a check for free: a declared total that is not a clean multiple of the single-unit volume points at the measuring or the counting rather than at the sum.
Density, and why LTL asks for it
Domestic less-than-truckload freight in North America is normally rated on density rather than on a volumetric divisor. Density is simply weight over volume, quoted in pounds per cubic foot: take the total weight of the piece, skid included, and divide by its volume in cubic feet.
A 48 × 40 × 48 inch skid is 53.33 cubic feet. At 600 lb that is 11.25 lb/ft³; at 900 lb the same skid is 16.88 lb/ft³. The volume has not changed and the freight has not changed shape — only the ratio the carrier reads.
This page gives you the volume half exactly, in both cubic metres and cubic feet, and the weight half from what you enter. The classification a carrier then applies to that density belongs to its tariff, changes, and is not something a calculator should guess at, so nothing here names one.
Density and volumetric weight are two answers to the same commercial problem — light freight taking up paid space — and they are not interchangeable. If a quote mentions a divisor, it is volumetric weight; if it asks for pounds per cubic foot, it is density.
Volumetric weight for air and courier
Where a divisor is used rather than a density, the shape is: volumetric weight (kg) = length (cm) × width (cm) × height (cm) × quantity ÷ divisor. Chargeable weight is then the greater of that and the actual gross weight.
Published divisors: 6000 is IATA's general rule for air cargo, 5000 is DHL Express's standard for its express products, 3000 corresponds to the 1:3 ratio on rail and 1000 to the 1:1 ratio on sea LCL. Road freight has no general rule; ratios differ by country and carrier.
A smaller divisor makes the same box heavier on paper. Ten cartons at 40 × 30 × 25 cm are 0.3 m³, or 300,000 cm³: 50 kg at a divisor of 6000, 60 kg at 5000, and 300 kg on the sea LCL ratio. If those cartons are 12 kg apiece, an airline bills the 120 kg actual weight while the same freight moving LCL is assessed at 300 kg.
Carriers change divisors, use different ones for different services, and some apply a minimum chargeable weight per piece. This page applies the divisor you pick across the whole shipment; one assessed piece by piece and rounded up each time lands a little higher.
Measuring a skid so the number survives the terminal
What is charged for is the space the unit occupies on the equipment, so measure the outside of the finished, wrapped unit — not the product, and not the carton's inside.
Measure after wrapping. A loaded skid bulges, and banding, corner boards and stretch film each add a little. Take the widest point, including any overhang past the deck.
Include the deck in the height. A four-foot load on a five-inch skid is a 53-inch unit, and the trailer has to take all of it.
Round up rather than down. The terminal rounds up when it re-measures, and a centimetre of optimism buys nothing.
Irregular items are charged on the rectangular space they need, so measure the box that would contain the item rather than the item itself.
Against a container
Ocean freight divides at roughly one container. Below it you buy space in a shared box and the rate comes per cubic metre or per freight ton, the freight ton being whichever is greater of one tonne and one cubic metre. Above it you book a container outright and the question becomes whether the cargo fits rather than what the volume costs.
Published internal volumes are where that question starts. Hapag-Lloyd's example specifications give 33.2 m³ for a 20ft, 67.7 m³ for a 40ft and 76.3 m³ for a 40ft high cube, and the carrier notes they are examples because containers differ by manufacturer.
Treat them as a ceiling nobody reaches. That volume assumes corner-to-corner packing with no gaps. Skid footprints leave dead space along the walls, freight cannot always be stacked to the roof without crushing, the door opening is narrower than the box, and the payload limit frequently bites first.
The container line in the result is therefore a share of a geometric volume and says so. Whether a load actually goes in is what a forwarder's load plan tells you.
Common mistakes
Rounding the unit conversion before cubing it. 0.025 m instead of 0.0254 m looks like a rounding decision and is a 4.7 % error once all three sides are multiplied.
The wrong power of ten. Centimetres become cubic metres by dividing by 1,000,000 and millimetres by 1,000,000,000, because the conversion is cubed with the dimensions.
Confusing density with volumetric weight. One is a ratio the carrier reads; the other is a weight the carrier bills. They are not two names for the same figure.
Averaging different piece sizes. Covered above, and easy to miss because the result looks perfectly reasonable.
Reading a container's capacity as loadable space. Internal volume measures an empty box; loading efficiency is a separate question, and palletised freight reaches well under it.
What this page does not know
It calculates volume and converts units. It holds no freight rates, no carrier tariff, no freight classification and no customs rule, and it cannot tell you what a shipment will cost. The cost line multiplies your volume by a rate you supply, leaving out minimum charges, accessorials, fuel surcharges, a freight-ton basis and everything else on a real invoice.
Volumetric weight is worked out across the whole shipment on the divisor you choose. A carrier may use a different one, assess each piece separately, or apply a minimum, so read the figure as a way of checking a quote rather than predicting one. Container capacities are geometric volumes from a published specification and say nothing about whether cargo will load.
Each edge is capped at 100 m and each line at 1,000,000 pieces, far past any real shipment and enough to keep the exact arithmetic instant. Everything runs in your browser and nothing you enter leaves the page.
Sources and methodology
Unit conversions are exact by definition and are implemented as exact ratios rather than decimal approximations: 1 inch = 2.54 cm and 1 foot = 0.3048 m exactly (NIST, Guide to the SI, Appendix B), and the litre is exactly one cubic decimetre, so 1 m³ = 1,000 L.
The 6000 divisor and the rule that the greater of actual and volumetric weight is billed come from IATA's material on air cargo tariffs and rules. The 5000 divisor is DHL Express's published standard. The 1:3 rail and 1:1 sea ratios, and the note that road ratios vary, come from DHL Global Forwarding's guide to chargeable weight.
Container capacities of 33.2 / 67.7 / 76.3 m³ are Hapag-Lloyd's published example specifications, quoted with that carrier's own caveat that specifications vary by manufacturer.
Density is defined here as weight divided by volume and nothing more. No freight classification is named or implied: classes sit in a carrier's tariff, are revised, and are not something a volume calculator is in a position to assert.
Every worked figure on this page is recalculated by tests/cbm-lib.test.js and checked there against a hand calculation.