CBM Calculator — Carton & Shipment Volume

What the calculator gives you

Type the packed size of a carton and how many of them you are shipping. You get the volume of one carton and of the whole consignment in cubic metres, the same figure in cubic feet and litres, and a line-by-line substitution you can check against your own arithmetic.

A shipment is rarely one carton size, so the form takes a line per size, each with its own unit. Ten cartons measured in centimetres and two crates measured in inches can sit in the same shipment and the totals still come out right. Behind the form every measurement is held as an exact fraction rather than a decimal approximation, which is why 40 × 30 × 25 cm × 10 reads as 0.3 m³ and not 0.30000000000000004.

Open the options panel and you can also compare actual weight with volumetric weight on a divisor you choose, turn the volume into a freight estimate using a rate you have been quoted, and see the shipment as a share of a container's internal volume.

What CBM means

CBM is shorthand for cubic metre, written m³. It is the standard way freight is measured by volume: a forwarder quoting sea LCL asks for CBM, an air quote starts from it, and a warehouse rate card is usually per CBM per month. One cubic metre is the space filled by a cube one metre on each side — 1,000 litres, or a 100 × 100 × 100 cm box.

Volume matters because space is what a carrier is selling. An aircraft hold and a container both run out of room long before they run out of weight allowance for light cargo, so a shipment of cushions and a shipment of bolts occupying the same space cost broadly the same to move even though one weighs twenty times the other. That is the whole reason the industry converts volume into a billable figure, which is the volumetric weight further down this page.

The formula, and a worked example

Work in metres and the formula has nothing hidden in it:

CBM = length (m) × width (m) × height (m) × quantity

Quantity is a plain multiplier, so doubling the carton count doubles the CBM and nothing else changes. That linearity is worth holding onto: if a quoted volume is not a clean multiple of the single-carton figure, the error is in the measurement or the count, not in the arithmetic.

From centimetres, millimetres, inches and feet

Every unit reduces to the same thing — get each side into metres, then multiply. The divisors people memorise are just that conversion done in advance:

The inch and foot figures are exact, not rounded off somewhere convenient: the international inch is defined as 2.54 cm and the foot as 0.3048 m exactly, so a cubic inch is exactly 0.000016387064 m³ and a cubic foot exactly 0.028316846592 m³. Those exact values are what the calculator uses.

Feet work the same way. A 4 × 3 × 2 ft crate is 24 ft³, and 24 × 0.028316846592 = 0.6796 m³. Because the ratio is exact in both directions, converting that answer back gives 24 ft³ again rather than 23.9999.

Several carton sizes in one shipment

Almost every real consignment has more than one size in it, and this is where a quick calculation usually goes wrong. The right method is to work out each size separately and add the volumes. The tempting shortcut — average the dimensions, multiply by the total piece count — is not an approximation, it is a different calculation with a different answer.

The same applies to units. Add one line in centimetres, one in inches and one in metres if that is how your supplier sent the packing list; each line is converted on its own before anything is added, so nothing is lost in a hurried conversion. If you are checking how much one line contributes to the whole, the percentage calculator will turn 1.92 out of 2.22 into a share.

CBM, cubic feet and litres

Three units for the same quantity, and packing lists move between them constantly. Litres are the easy one: a litre is exactly a cubic decimetre, so 1 m³ is exactly 1,000 L and the conversion is a decimal point. Cubic feet are the one worth writing down — 1 m³ = 35.3147 ft³, and going the other way, 1 ft³ = 0.0283 m³.

Cubic feet appear on this page as ft³, though in South Asian freight paperwork the same unit is very often written CFT. It is the same measurement; only the abbreviation differs. The conversion block above the article converts between all three directly if that is all you need.

Volumetric weight and chargeable weight

Volumetric weight — dimensional weight, DIM weight — is volume expressed in kilograms so that it can be compared with real weight. The carrier divides the shipment's size in cubic centimetres by a number it publishes:

Volumetric weight (kg) = L (cm) × W (cm) × H (cm) × quantity ÷ divisor

Chargeable weight is the greater of the actual weight and the volumetric weight. Dense cargo is billed on what it weighs; light, bulky cargo on the room it takes up. That "whichever is greater" rule is the part that is genuinely universal; the divisor is not.

A smaller divisor produces a larger volumetric weight for the same box, which is why the difference is worth checking before you accept a quote. Our ten-carton example is 0.3 m³ — 300,000 cm³ — so it is 50 kg on a 6000 divisor, 60 kg on 5000, and 300 kg on the sea LCL 1:1 ratio. If those cartons actually weigh 12 kg each, the real weight of 120 kg is what an airline would bill, but the same shipment moving LCL would be assessed on 300 kg.

Two cautions. Carriers change divisors, apply different ones to different services, and some apply a minimum chargeable weight per piece as well — so the divisor selector on this page is a choice you make with your rate sheet in front of you, not a lookup. And the tool applies your divisor to the whole shipment; a carrier that assesses each piece separately and rounds each one up will arrive at a slightly higher figure.

CBM at sea: LCL, FCL and container capacity

Sea freight splits at roughly one container's worth of cargo. Below that you buy space inside a shared container — LCL, less than container load — and the rate is quoted 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 whole container (FCL) at a flat rate, and the volume stops driving the price directly: what matters then is whether the cargo fits.

Published internal volumes give a starting point for that question. Hapag-Lloyd's example specifications put a 20' standard at 33.2 m³, a 40' standard at 67.7 m³ and a 40' high cube at 76.3 m³ — and that carrier's own page notes the figures are examples, because containers vary by manufacturer.

Treat them as a ceiling nobody reaches. That volume assumes the box is filled corner to corner with no gaps, which cargo never is. Pallet footprints leave dead space along the walls, cartons cannot always be stacked to full height without crushing, the door aperture is narrower than the container, and the payload limit can stop you long before the volume does. The container line in the result is a share of a geometric volume, and it says so; a forwarder's load plan is what tells you whether a shipment actually fits.

Measuring a carton so the number is right

The volume a carrier charges for is the space the package occupies on their equipment, so measure the outside of the finished, packed carton — not the product, and not the carton's internal capacity.

• Measure after packing. A carton bulges once it is full, and strapping, corner protectors and shrink wrap all add a little. Measure at the widest point.
• Include the pallet. If the cartons ship palletised, the pallet's footprint and height are part of the shipment. Enter the loaded pallet as its own line rather than the cartons on it.
• Round up, not down. A carrier measuring at the terminal will round up, and there is no upside to a figure that is optimistic by a centimetre.
• Irregular shapes take their bounding box. A cylinder or an odd-shaped crate is charged on the rectangular space it needs, not on the shape itself.
• Keep sizes separate. One line per size, always. Two sizes averaged into one is the single most common way a volume comes out wrong.

Common mistakes

Dividing by the wrong power of ten

Centimetres go to cubic metres by 1,000,000 and millimetres by 1,000,000,000 — because the conversion is cubed. Dividing centimetres by 100, or millimetres by 1,000, is a factor of ten thousand out and gives an answer that is obviously wrong once you look at it.

Using the product's dimensions

The item inside the box is not what ships. Packaging, void fill and the carton walls all add volume that a carrier charges for.

Confusing CBM with volumetric weight

CBM is a volume and volumetric weight is a weight. They are related by a divisor the carrier chooses, so a shipment has one CBM figure and as many volumetric weights as there are divisors.

Averaging different carton sizes

Covered above, and worth repeating because it does not look like an error. Add the sizes, never blend them.

Treating a container's capacity as usable space

Internal volume is what an empty box measures. Loading efficiency is a separate question, and for palletised cargo the practical figure is a good deal lower.

Limitations

This tool works out volume and converts it. It knows no freight rates, no carrier tariffs and no country's customs rules, and it cannot tell you what a shipment will cost. The cost line multiplies your volume by a rate you supply, which leaves out minimum charges, surcharges, a freight-ton basis, local handling and everything else on a real invoice.

The volumetric weight is calculated from the whole shipment on the divisor you pick. A carrier may use a different divisor, assess each piece separately, or apply a minimum chargeable weight, so treat the figure as a check on a quote rather than a prediction of one. Container capacities are geometric volumes from a published specification and say nothing about whether cargo will fit.

Each carton edge is limited to 100 m and each line to 1,000,000 pieces, which is well past any real shipment and keeps the exact arithmetic instant. Everything runs in your browser; nothing you type leaves the page.

Sources and methodology

Unit conversions are exact by definition and are implemented as exact ratios, not decimal approximations: 1 in = 2.54 cm and 1 ft = 0.3048 m exactly, and the litre is exactly one cubic decimetre, so 1 m³ = 1,000 L. Every worked example on this page is re-checked by tests/cbm-lib.test.js against a hand calculation, so the prose and the calculator cannot drift apart.

• NIST Guide to the SI, Appendix B: Conversion Factors — the exact inch, foot and cubic-foot factors used throughout.
• Air Cargo Tariffs and Rules — IATA, for the general air-cargo rule of dividing cubic centimetres by 6,000 and billing on whichever of actual and volumetric weight is higher.
• Weight and Dimensions — DHL Express, for the 5,000 divisor used on express products.
• Calculating Chargeable Weight by Air, Ocean, Road and Rail — DHL Global Forwarding, for the 1:6, 1:3 and 1:1 density ratios and the note that road ratios vary by carrier.
• Container specifications — Hapag-Lloyd, for the 33.2 / 67.7 / 76.3 m³ example capacities, published with that carrier's own note that specifications vary by manufacturer.

Frequently asked questions