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CBM Calculator

Enter carton length, width and height in centimetres plus the number of cartons to get per-carton and total volume in CBM, with loading estimates for 20GP, 40GP, 40HQ and 45HQ based on conservative usable capacity.

Almost every export quote starts with the same question: how many cubic metres is this shipment? Forwarders price sea freight by CBM, factories pick the container type by CBM, and all you usually have on hand are the carton dimensions and the carton count.

The figures here are capacity estimates. Container capacities are taken at conservative usable values (about 28 m³ for a 20GP) and ignore pallet footprints, stacking gaps and optimal packing patterns. Treat them as planning numbers: confirm the final loading with your forwarder, and if the goods go on pallets, enter the pallet footprint itself.

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How to use

  1. Measure one carton length, width and height in centimetres, outside dimensions included.
  2. Enter the number of cartons; for palletised cargo enter the pallet footprint and the number of pallets.
  3. Read per-carton volume, total CBM, and how many cartons fit a 20GP and a 40HQ.
  4. When the shipment exceeds one container, the result shows roughly how many 40HQ containers you need for the quote.

How it works

What CBM is and how to work it out

CBM stands for cubic metre and is the standard volume unit in international freight. Multiply carton length, width and height to get per-carton CBM - if you measure in centimetres, divide the product by one million. A 60 x 40 x 40 cm carton is 0.096 m³, so 100 cartons come to 9.6 m³.

Which container capacity to plan with

The capacities used here are deliberately conservative: 28 m³ for a 20GP, 58 m³ for a 40GP, 68 m³ for a 40HQ and 76 m³ for a 45HQ. Theoretical volumes are larger, but door frames, corrugation and stacking gaps cut into them; planning with conservative numbers avoids booking a container the cargo will not fit into.

Palletised cargo

Do not calculate palletised cargo per carton. Pallets occupy volume themselves and usually cannot be stacked, so enter the full pallet dimensions including the goods and count each pallet as one unit. If pallets are double stacked, include both layers in the count. Some lanes also charge on weight, so check the chargeable weight alongside the volume.

Code example

JavaScript Centimetres to CBM 

// dimensions in cm; 1 m³ = 1,000,000 cm³
const each = (l * w * h) / 1e6;
const total = each * cartons;

// a 60 x 40 x 40 cm carton:
// each = 96000 / 1e6 = 0.096 m³; 100 cartons = 9.6 m³

Python Estimating containers from conservative capacity 

CAPACITY = {"20GP": 28, "40GP": 58, "40HQ": 68, "45HQ": 76}   # m³

def containers(total_cbm, kind="40HQ"):
    return -(-total_cbm // CAPACITY[kind])   # round up

def cartons_per_container(each_cbm, kind="20GP"):
    return int(CAPACITY[kind] // each_cbm)   # round down

containers(288, "40HQ")          # 5 containers
cartons_per_container(0.096)     # 291 cartons in a 20GP

FAQ

How do I calculate CBM?

Multiply carton length, width and height in metres to get per-carton CBM; measuring in centimetres, multiply first and divide by 1,000,000. For example 60 x 40 x 40 cm equals 0.096 CBM, so 100 cartons are 9.6 CBM. Irregular shapes measured at the longest edge give a slightly generous estimate.

How much fits in a 20GP container?

At the conservative 28 m³ usable capacity used here, it depends on carton size: roughly 291 cartons of 0.096 m³. Real loading varies with how regular the cartons are, whether they are palletised and how they are stacked, so confirm with the loading plan.

What is the difference between a 40HQ and a 40GP?

A 40HQ is about 30 cm taller, which this tool estimates as 68 m³ against 58 m³ - roughly 10 m³ more. For the same shipment a 40HQ often saves a whole container and is usually better value, so it is worth pricing both.

Why is the carton count lower than the theoretical maximum?

Because conservative usable capacity is used and packing optimisation is ignored: carton dimensions rarely tile a container exactly and the leftover gaps cannot be used. Real load factors typically run 85% to 95%, so a well-planned loading scheme may beat this estimate slightly.

How do I handle palletised cargo?

Enter the full pallet dimensions including the goods as the carton size and the number of pallets as the count. A standard pallet is about 120 x 100 x 150 cm loaded, roughly 1.8 m³. Pallets normally cannot be stacked, so check that the container height has room for loading clearance.

What if the cargo is very heavy - can volume alone run past the limit?

Yes. Containers have payload limits, around 28 tonnes for a 20GP and 26 tonnes for a 40HQ, and dense cargo hits the weight limit before the volume limit. This tool covers volume only, so check total weight when quoting or booking and plan to whichever limit binds first.

Is CBM used for LCL shipments too?

Yes, and LCL is charged almost entirely by CBM, usually with a minimum chargeable volume such as one cubic metre. Small shipments of a few dozen kilograms can sometimes ship cheaper by weight, so compare both bases before deciding.

Is my data uploaded anywhere?

No. Everything is calculated in your browser: carton dimensions and counts never leave your device, and the tool works offline.