Shipping goods internationally? Freight forwarders quote in CBM (cubic meters)— not kilograms alone. Whether you are exporting handicrafts from India, importing machinery from China, or planning your first FCL shipment, knowing your total CBM decides container size, LCL vs FCL cost, and whether your cargo actually fits. This guide explains the CBM formula, 20ft vs 40ft container capacity, and how to use Pitara's free CBM calculator for carton and container planning.
What is CBM in shipping?
CBM stands for cubic meter — the standard volume unit in ocean freight. Freight rates for LCL (Less than Container Load) shipments are often priced per CBM. Even for FCL (Full Container Load), knowing your CBM helps you choose between a 20ft and 40ft container and avoid paying for empty space you do not need.
Volume matters because ships and containers have space limits separate from weight limits. Light but bulky cargo (furniture, textiles, empty plastic goods) fills a container by volume before hitting weight capacity. Heavy dense cargo (steel, machinery) may hit weight limits first.
CBM calculation formula
For a single carton measured in centimetres:
CBM = (Length × Width × Height in cm) ÷ 1,000,000
Example: a carton 60 cm × 40 cm × 30 cm = 72,000 cm³ ÷ 1,000,000 = 0.072 CBM per box. For 100 identical cartons: 0.072 × 100 = 7.2 CBM total.
If dimensions are in inches, convert first: 1 inch = 2.54 cm. Or use Pitara's CBM Calculator with the inches toggle — it converts internally.
20ft vs 40ft container — how much CBM fits?
Standard shipping container usable volumes (approximate, varies by cargo type and loading):
- 20ft container: ~33 CBM usable space, max payload ~28,000 kg
- 40ft container: ~67 CBM usable space, max payload ~26,500 kg
- 40ft High Cube: ~76 CBM — extra height for bulky cargo
Real loading never reaches 100% of theoretical CBM — gaps between cartons, pallets, and irregular shapes reduce usable space. Plan for 85–90% of rated capacity as a practical maximum. Pitara's calculator shows how your shipment CBM compares to 20ft and 40ft benchmarks.
Step-by-step: calculate shipment CBM
- Open CBM Calculator.
- Enter carton length, width, and height (cm or inches).
- Set quantity — number of identical cartons in the shipment.
- Read total CBM and the 20ft/40ft container comparison.
- Repeat for different carton sizes if your shipment has mixed packaging.
For mixed carton sizes, calculate each SKU separately and add the CBM totals together.
FCL vs LCL — when CBM decides
LCL: You share container space with other shippers. Charged per CBM (or per ton, whichever is higher). Economical below ~15 CBM for most trade lanes.
FCL: You book an entire container. Fixed rate regardless of how full it is. Makes sense when your cargo exceeds ~15–20 CBM or you need dedicated space for fragile or high-value goods.
If your total is 25 CBM, a 20ft FCL (33 CBM) is likely cheaper than LCL. At 8 CBM, LCL usually wins. Always compare quotes from your freight forwarder — CBM gives you the starting point for that conversation.
CBM vs weight — chargeable weight
Ocean freight uses chargeable weight: the higher of actual weight or volumetric weight. For sea freight, volumetric weight (kg) ≈ CBM × 1,000. A shipment of 5 CBM weighing only 800 kg may still be charged at 5,000 kg equivalent for LCL pricing. Always provide both weight and CBM to your forwarder.
Tips for accurate CBM planning
- Measure outer carton dimensions, not inner product size
- Include pallet height if goods ship on pallets
- Add 2–3 cm per side for packing material if measuring product only
- Non-stackable cargo may need extra space — discuss with forwarder
- Round up slightly — underestimating CBM leads to freight surprises
CBM in the full import-export workflow
CBM is one piece of the puzzle. Pair it with:
- Landed Cost Calculator — freight cost + duty + charges per unit
- Customs Duty Calculator — BCD, SWS, IGST breakdown
- Currency Converter — convert freight quotes to INR
- Unit Converter — cm to inches, kg to lbs
Explore all calculators on the Import/Export & Logistics hub — built for Indian traders and freight forwarders.
Calculate your shipment CBM now: CBM Calculator — free, instant, runs in your browser.
Frequently Asked Questions
How is CBM calculated?
CBM = (Length × Width × Height in cm) ÷ 1,000,000. Multiply by the number of cartons for total shipment volume.
How many CBM fit in a 20ft container?
A 20ft container holds roughly 33 CBM usable space; a 40ft holds about 67 CBM.
Can I use inches instead of cm?
Yes. Switch to inches in the calculator and it converts internally.
When should I choose FCL over LCL?
FCL is usually economical above 15–20 CBM. Below that, LCL charged per CBM is often cheaper.
What is chargeable weight in shipping?
Freight uses the higher of actual weight or volumetric weight (CBM × 1,000 kg for sea freight).
Should I measure inner product or outer carton?
Always measure outer carton dimensions including packaging for accurate CBM.
Try it free
Use our CBM Calculator tool — runs in your browser, no upload required.
Open CBM Calculator