CBM Calculator — size, cost & ship your cargo

What CBM actually is

CBM = cubic meter — the volume of your shipment. One carton's CBM is its length × width × height in centimeters, divided by 1,000,000. Multiply by the number of cartons to get your total shipment volume, which is what sea-freight rates are usually quoted on.

Why chargeable weight matters for air

Air freight bills on chargeable weight = the greater of actual gross weight and volumetric weight. Volumetric weight is your dimensions divided by a divisor (6,000 for most express couriers, 5,000 for some airlines) per carton. A big but light carton can be "heavier" on paper than a small dense one — this is where air quotes surprise sellers. Switch the result to Sea mode to see the CBM-based figure ocean freight is quoted on instead.

How LCL freight is charged (the W/M rule)

LCL (less-than-container load) ships your goods with others and you pay per CBM — but the rate is applied to the chargeable volume, which is the greater of your actual volume and your weight converted at 1 CBM = 1,000 kg. That's the W/M rule (weight or measurement): a dense, heavy shipment is billed on its weight, a light, bulky one on its volume — whichever is larger. This calculator shows the chargeable volume and an estimated cost the moment you pick a lane or type your forwarder's rate. Use it to sanity-check a quote before you book.

How many cartons fit a container

A 20ft container holds roughly 28 CBM of usable space (and ~21,000 kg), a 40ft about 58 CBM (~26,700 kg), and a 40ft High Cube about 68 CBM. We divide each limit by your single-carton volume and weight, take the lower number, and tell you how many full containers your order needs. We apply a realistic load factor (default 85%) so the count reflects how cartons actually stack — not a perfect-fit ideal — and weight often caps you before volume does.

Works as your container load calculator

Whether you're planning an Alibaba consolidation, a 1688 container, or a courier air shipment, the same math applies. Use it as a CBM calculator, a container load calculator, and a quick check for how many cartons fit in a 20ft container before you book space. Shipping a mixed order? Switch to Batch / multi-SKU and enter each product line — totals, LCL cost and the container plan roll up automatically.

What goes on your packing list & commercial invoice

Customs and your buyer want the same numbers you just calculated: total packages, total gross weight, and total volume, plus per-package dimensions. The Copy packing list button outputs exactly that block — ready to paste into your packing list, commercial invoice or declaration. Add each product's HS code in the batch table and it travels with the line, which is also what the HS Code Lookup tool is for when you need to find it.

Worked example — a mixed LCL order

Two SKUs: 300 cartons of 40×30×25 cm / 8 kg, plus 200 cartons of 50×40×30 cm / 12 kg (at the default 85% load factor):

Example uses an 85% load factor and a $45/CBM example lane rate — adjust both in the calculator for your own shipment.

Sources & method

Container capacities reflect common usable limits — a 20ft container is nominally ~33 m³ but practical loading is ~28 m³ after accounting for pallets and the curved walls; 40ft ~58 m³ and 40ft HC ~68 m³. Air volumetric divisors follow IATA practice (6,000 for express, 5,000 for some passenger airlines). LCL chargeable volume uses the W/M rule at 1 CBM = 1,000 kg. The container fit uses each limit × the load factor you set (default 0.85) ÷ your single-carton volume and weight. Exact allowances vary by carrier and commodity — confirm with your freight forwarder for a firm quote.