CBM calculator

How to use this CBM calculator

Enter the length, width and height of one carton, then how many of that carton you are shipping. The total appears immediately - there is no calculate button, and the arithmetic that produced the number is printed underneath it so you can check every step.

If your packing list has more than one carton size, press Add another carton size and enter the next one. Sizes are totalled together, and the result shows how many cartons and how many distinct sizes went into the figure.

The weight field on each row is optional. Fill it in and you also get the shipment weight, plus a warning when your cargo is dense enough that an LCL carrier would bill you on weight rather than volume.

Using the CBM calculator in cm

Centimetres are the default because that is how most factory packing lists are written. The conversion is a single division:

CBM = (Length x Width x Height in cm) / 1,000,000

The divisor is not a shipping constant. A metre is 100 centimetres, so a cubic metre is 100 x 100 x 100 = 1,000,000 cubic centimetres, and dividing by a million simply converts cm3 to m3. It does not vary by carrier, by lane, or by commodity, and it is never going to be revised.

A 40 x 30 x 25 cm carton is 30,000 cm3, which is 0.03 CBM. One hundred of them is 3.000 CBM.

Using the CBM calculator in inches

Switch the Dimensions in selector to inches and enter your figures exactly as measured. The calculator converts each dimension to centimetres first, then applies the same division, which is why you must not mix units within one shipment.

To run the CBM calculator from inches by hand instead, the shortcut is:

CBM = (Length x Width x Height in inches) / 61,024

That divisor comes from the unit conversion itself - one inch is 2.54 cm, so a cubic metre is 100 / 2.54 cubed, which is 61,023.7 cubic inches. Rounding to 61,024 is accurate to well under a tenth of a per cent.

A 16 x 12 x 10 inch carton is 1,920 cubic inches, or about 0.0315 CBM. One hundred of them comes to 3.146 CBM - very close to the metric example above, because 16 x 12 x 10 inches is roughly a 40 x 30 x 25 cm box.

Feet and metres are available in the same selector for anyone working from a container drawing rather than a carton label.

Worked example: three carton sizes

You are shipping a mixed order with three sizes on the packing list:

• 60 cartons at 40 x 30 x 25 cm
• 24 cartons at 60 x 40 x 40 cm
• 8 cartons at 120 x 80 x 60 cm

Take them one at a time.

Size 1. 40 x 30 x 25 = 30,000 cm3, so 0.03 m3 per carton. Sixty of them is 1.800 m3.

Size 2. 60 x 40 x 40 = 96,000 cm3, so 0.096 m3 per carton. Twenty-four is 2.304 m3.

Size 3. 120 x 80 x 60 = 576,000 cm3, so 0.576 m3 per carton. Eight is 4.608 m3.

Added together: 1.800 + 2.304 + 4.608 = 8.712 m3 across 92 cartons.

Now look at what averaging would have done. The mean carton is roughly 73 x 50 x 42 cm, about 0.153 m3, and 92 of those is 14.1 CBM - over sixty per cent too high. Averaging carton dimensions is not a shortcut, it is a different and wrong calculation, and it is the single biggest reason a one-box CBM calculator is not much use on a real packing list.

Container CBM calculator: will your shipment fit?

Once you have a total, the obvious next question is whether it fits a container. Carrier-published internal volumes are about 33 CBM for a 20ft and about 67 CBM for a 40ft, with a 40ft high cube higher again. The two carriers cited at the foot of this page publish 33.1 and 33.2 for the 20ft, and 67.6 and 67.5 for the 40ft, which is the level of agreement to expect - close, but not a single number.

Treat those as ceilings you will never reach. Real loading typically lands ten to fifteen per cent below the theoretical figure, because cartons do not tessellate perfectly, pallets waste floor space, and stacking height is limited by carton crush strength rather than by the roof. An 8.712 CBM shipment is comfortably LCL; a 30 CBM shipment is not a 20ft container even though the arithmetic says it nearly fits.

Volume is also only one of two limits. A container has a payload limit as well as a cubic capacity, and dense cargo - tiles, fasteners, liquids - hits maximum weight with the box half empty. A CBM figure answers “how much space”, never “will it ship”.

Pallet CBM calculator: measuring a palletised load

If your cargo is going on pallets, measure the loaded pallet, not the cartons. A carrier charges for the footprint and height the pallet occupies on the vessel, and that includes the pallet deck itself.

For a standard 120 x 100 cm pallet loaded to 150 cm total height, the calculation is 120 x 100 x 150 / 1,000,000 = 1.8 CBM per pallet. Enter the loaded pallet as one row with the pallet count as the quantity, and the total is your palletised shipment volume.

This will read higher than the sum of the cartons on it, and that gap is real rather than an error - it is the air between cartons and the pallet deck underneath, and you are paying to ship both.

Measure the carton, not the product

The most common mistake in a CBM calculation is measuring the product rather than the packed carton. The carrier charges for the space the box occupies, which includes the corrugate, the void fill, and any lid sitting proud of the walls.

If your supplier gives you dimensions, check whether they are quoting the product, the inner carton, or the master carton. The difference between an inner and a master carton is routinely a factor of six or twelve, and a CBM figure built on the wrong one will not survive first contact with a forwarder’s quote.

Why this is a real CBM calculator

Most free shipping CBM calculators accept one carton size, print one number, and show none of the arithmetic. That is fine for a homework question and close to useless for a shipment.

This one takes as many sizes as your packing list has, prints the working line by line so you can check it or paste it into an email, converts cleanly between cm, metres, inches and feet, and flags when weight rather than volume is going to drive your bill. It also writes your inputs into the page address as you type, so copying the link sends the exact result you are looking at to your supplier or forwarder, already filled in.

A free CBM calculator online, with nothing to install

There is no signup, no account and no paid tier. The calculator runs entirely in your own browser as plain JavaScript - your carton dimensions, quantities and weights are never transmitted anywhere, because there is no server to transmit them to.

That matters more than it sounds for freight. Carton counts and shipment volumes describe an order that may not be public yet, and the safest way to handle commercially sensitive numbers is to never receive them.