How do I calculate CBM?

CBM (cubic metres) is calculated by multiplying length × width × height in metres. If your dimensions are in centimetres, multiply L × W × H in cm and divide by 1,000,000. For example, a carton 80cm × 60cm × 50cm has a volume of 240,000 cm³, which is 0.24 CBM.

How is LCL freight calculated from CBM?

LCL (Less than Container Load) sea freight is charged on the greater of actual weight in tonnes or volume in CBM (where 1 CBM = 1 tonne for chargeable purposes). So if your shipment is 3 CBM weighing 1,200 kg, you'll be charged for 3 CBM. If it's 3 CBM weighing 4,500 kg, you'll be charged for 4.5 tonnes.

How many CBM fits in a 40ft container?

A 40ft standard container has approximately 67 CBM of internal capacity, and a 40ft High Cube (HC) has approximately 76 CBM. In practice, packing efficiency reduces usable capacity to around 85-90% of nominal volume — so plan for around 57-60 CBM in a 40ft and 65-68 CBM in a 40ft HC. A 20ft container fits approximately 28-30 CBM in practice.

When does FCL become cheaper than LCL?

As a rough rule, when your LCL shipment exceeds 12-15 CBM, booking a full 20ft FCL container usually becomes more cost-effective on Asia-UK routes. The exact crossover depends on the lane, freight rates, and destination charges. Always compare both quotes for shipments in the 10-20 CBM range.

CBM Calculator — Sea Freight Cubic Metre & Container Fit

📦 CBM & Container Fit Calculator

Length

Width

Height

No. of pieces / cartons

Total weight (kg, optional)

Enter dimensions and click Calculate to see CBM, LCL chargeable weight, and container fit estimates.

What is CBM?

CBM (cubic metres, written as m³) is the standard unit of volume in international sea freight. Quoted on every LCL booking, used by carriers to allocate space, and the basis on which less-than-container-load freight rates are calculated.

The formula is simple — Length × Width × Height, all in metres. If your dimensions are in centimetres, the easiest method is to multiply L × W × H in cm then divide by 1,000,000 (the number of cubic centimetres in a cubic metre).

Quick formula: CBM = (L × W × H in cm) ÷ 1,000,000
Or: CBM = (L × W × H in m)

Why CBM matters in sea freight

Sea freight has two pricing realities. FCL (Full Container Load) is priced per container — once you've booked the box, you can fill it. LCL (Less than Container Load) is priced on the greater of weight (in tonnes) or volume (in CBM). The shipping line charges whichever is higher.

This "weight or measure" principle means a dense, heavy shipment of small volume might be charged on weight; a light, bulky shipment of large volume is charged on CBM. The carrier always wins.

LCL chargeable weight — the 1 CBM = 1 tonne rule

For LCL sea freight, the conversion is:

1 CBM = 1,000 kg (1 tonne) chargeable

If your shipment is 3 CBM weighing 1,200 kg, the volumetric chargeable weight is 3 tonnes; the actual weight is 1.2 tonnes; you'll be charged on 3 tonnes/CBM.

If your shipment is 3 CBM weighing 4,500 kg, the actual weight is 4.5 tonnes (above the volumetric); you'll be charged on 4.5 tonnes.

Air vs sea volumetric: Don't confuse the two. Airfreight uses ÷6,000 (i.e. 1 cm³ per 6 kg of volumetric weight). Sea LCL uses 1 CBM = 1,000 kg. See our volumetric weight guide for the full picture.

Container capacities — usable CBM

Nominal vs realistic container capacities. The "nominal" figure is the geometric internal volume; "realistic" assumes typical 85-90% packing efficiency once you account for pallet sizes, securing space, and the shape of your cargo.

Container type	Nominal CBM	Realistic packing	Max payload
20ft Dry	~33 CBM	~28-30 CBM	~28,000 kg
40ft Dry	~67 CBM	~57-60 CBM	~28,800 kg
40ft High Cube (HC)	~76 CBM	~65-68 CBM	~28,600 kg
45ft High Cube	~86 CBM	~73-76 CBM	~27,700 kg
20ft Reefer	~28 CBM	~24-26 CBM	~27,400 kg
40ft Reefer HC	~67 CBM	~57-60 CBM	~26,500 kg

When LCL stops being cheaper than FCL

LCL is competitive for small shipments. But because LCL is charged per CBM with origin/destination handling fees on top, the cost-per-CBM rises sharply on larger consignments. At some point, booking a full 20ft FCL container is cheaper — even with empty space.

Up to ~5 CBM: LCL is normally far cheaper
5–12 CBM: LCL still wins on most lanes, but check both
12–15 CBM: Crossover zone — 20ft FCL often becomes equal or cheaper, plus you avoid CFS handling charges and consolidation transit delays
15+ CBM: 20ft FCL almost always wins; over ~28 CBM go straight to FCL
28+ CBM: Consider 40ft FCL; the per-CBM rate drops materially

Always get both quotes: For any shipment in the 8–20 CBM range, ask your forwarder for both an LCL and 20ft FCL quote. FCL wins more often than people expect once destination charges are included.

Common CBM calculation mistakes

Measuring goods only, not the carton. Use outer carton dimensions including any over-wrap or pallet height
Mixing cm and m. Stick to one unit and convert at the end
Forgetting pallet height. A standard UK pallet is 14.4 cm; a Euro pallet is similar. Add this to your carton stack height if shipping palletised
Rounding down. Always round dimensions up — that's what carriers do
Quoting "approximate" CBM. Carriers will re-measure and rebill — accurate figures up front avoid surprise invoices
Not adding all cartons. For mixed shipments, calculate CBM per carton type then sum

Worked examples

Example 1 — Single carton

Carton 80 × 60 × 50 cm:

CBM = (80 × 60 × 50) ÷ 1,000,000 = 0.24 CBM
LCL chargeable weight (volumetric): 240 kg

Example 2 — Pallet shipment

10 cartons each 60 × 40 × 40 cm, total weight 320 kg:

CBM per carton = (60 × 40 × 40) ÷ 1,000,000 = 0.096 CBM
Total CBM = 0.96 CBM
LCL chargeable (volumetric) = 960 kg; actual = 320 kg → chargeable: 960 kg (volumetric wins)

Example 3 — Stuffing a 40ft HC

You have 380 cartons each 50 × 40 × 50 cm:

CBM per carton = 0.10 CBM
Total CBM = 38.0 CBM
40ft HC realistic packing capacity ~65-68 CBM — plenty of space
20ft realistic packing ~28-30 CBM — too small for 38 CBM
Decision: 40ft HC FCL

Practical shipment example: A pallet that overhangs by a few centimetres can be charged on the larger footprint, and stackability changes the quote. Measure the freight as it will actually be handed to the carrier, not the theoretical carton size from the supplier's catalogue.

Related calculators & guides

Volumetric weight calculator — for airfreight and courier
Chargeable weight calculator — air/courier standalone
Freight density calculator — kg/m³ analysis
Landed cost calculator — full UK landed cost
Sea Freight A–Z — full glossary