CBM Calculator

What is CBM in shipping?

CBM — cubic meter — is the unit the entire freight industry uses to describe how much space your cargo occupies. One CBM is a cube one meter on each side. When a Chinese factory tells you an order is “36 CBM, 500 cartons, 9,000 kg,” those three numbers decide almost everything about your shipping bill: whether you book LCL (priced per CBM) or your own container, which container size you need, and what the chargeable weight would be if you flew part of the order by air.

For builders and importers buying building materials from China, CBM is the first number to pin down — before freight quotes, before landed cost. A supplier's packing list gives you carton dimensions and quantities; this calculator turns that into total volume, weight, and a realistic container plan. If a supplier cannot give you carton dimensions and gross weights, treat it as a red flag: accurate packing data is table stakes for any factory that exports regularly.

CBM formula: how to calculate CBM

The CBM formula is simple multiplication with a unit conversion:

CBM per carton = (length cm × width cm × height cm) ÷ 1,000,000

Total CBM = CBM per carton × number of cartons

Measuring in inches? Convert first (1 inch = 2.54 cm) or divide the cubic-inch product by 61,024 — the calculator's unit toggle handles this for you. Worked example: a tile factory packs porcelain tile in cartons of 60 × 40 × 12 cm, 800 cartons total.

• Volume per carton: 60 × 40 × 12 = 28,800 cm³
• CBM per carton: 28,800 ÷ 1,000,000 = 0.0288 CBM
• Total: 0.0288 × 800 = 23.04 CBM

At 23 CBM the order fits a 20ft container with a few CBM to spare — or it might make more sense as LCL, depending on the lane. That is exactly the kind of decision the number exists to support. If your order mixes carton sizes (tile plus trim profiles plus adhesive, say), calculate each line separately and sum them — which is why this tool supports multiple line items instead of a single box.

Container capacity: theoretical vs practical CBM

Every container has two capacities: the theoretical internal volume printed in spec sheets, and the practical volume you can actually load once real cartons, void space, and loading ergonomics get involved. Confusing the two is the single most common CBM planning error.

Two practical notes. First, heavy building materials often hit the weight limit before the volume limit: a 20ft container maxes out around 28 tonnes of payload, which dense cargo like porcelain tile or natural stone reaches at well under 28 CBM. Second, palletized loads fit noticeably less than loose-loaded cartons — pallet decks, stacking limits, and footprint overhang can eat 10–20% of usable volume. This calculator flags container fit using practical carton capacities; your forwarder's load plan is the final word.

Volumetric weight: how carriers actually bill you

Carriers sell space as much as they carry weight, so light-but-bulky cargo is billed by volumetric weight — a converted weight based on volume — whenever it exceeds the scale weight. The number that ends up on the invoice is the chargeable weight: the greater of actual and volumetric.

• Sea LCL — 1 CBM : 1,000 kg. LCL is priced per “revenue ton,” the greater of CBM and weight in tonnes. Most building materials are dense enough that CBM governs anyway, but very heavy items (stone slabs, cast hardware) can flip to weight-based billing.
• Air freight — cm³ ÷ 6,000, i.e. 1 CBM ≈ 167 kg. A shipment of 2 CBM of lightweight aluminum grilles weighing 150 kg has a volumetric weight of about 334 kg — and 334 kg is what the airline bills, more than double the scale weight.
• Express couriers — cm³ ÷ 5,000, i.e. 1 CBM = 200 kg. DHL/UPS/FedEx use a harsher divisor than airlines, so bulky samples cost even more per actual kilogram.

The results panel above shows both bases so you can see instantly whether your cargo is “volume cargo” or “weight cargo” — which in turn tells you whether repacking into tighter cartons would actually cut your freight bill.

Common CBM mistakes

• Planning against theoretical capacity (33 / 67 / 76 CBM). Real carton loads achieve roughly 26–28, 54–58, and 65–68 CBM. Book a “33 CBM” order into a 20ft and you will be re-quoting freight at the worst possible moment.
• Forgetting that pallets eat space. Palletizing protects fragile goods like sanitary ware and glass, but the pallet base, stacking limits, and overhang typically cost 10–20% of container volume. Decide loose vs palletized before you size the container.
• Averaging mixed carton sizes. An order with three carton specs needs three line-item calculations, not one “average” carton. Small rounding errors multiply across hundreds of cartons.
• Measuring the product, not the export carton. Freight is billed on outer carton dimensions including padding and double-walling — often 2–5 cm larger per side than the product box.
• Ignoring the weight limit. Dense building materials frequently max out container payload before volume. Check total kg against ~28,000 kg (20ft) and ~26,500 kg (40ft/40HQ).
• Trusting a verbal “it fits.” Ask the factory for a packing list with carton dimensions, carton count, gross weight, and CBM per line — then verify it here before booking.

CBM questions importers ask

From CBM to freight cost to landed cost

CBM is step one of the import math chain. Once you know your volume, run it through the freight cost estimator to get a planning-level shipping range for your lane, then drop the freight number into the landed cost calculator to see the true per-unit cost with duty, brokerage, and delivery included. If you are earlier in the process, the guide to importing building materials from China maps the whole sequence, and the supplier directory is where the packing lists come from. Ready for real numbers? Submit an RFQ and ask every factory for carton dimensions, carton count, and gross weight up front.