Reference
Volumetric Weight & Cubic Measurement Explained
How cubic size drives freight cost across air, courier and ocean LCL — the CBM and volumetric-weight formulas, with worked examples for each mode.
Freight quotes can account for both mass and the space cargo occupies, but the conversion, comparison, rounding and minimums differ by carrier and service. This reference gives planning examples; the booked quote controls the chargeable basis.
Key takeaways
- Cubic metres (CBM) = length × width × height in metres. This single figure drives volume-based pricing in every mode.
- For planning, air freight is often estimated at cm³ ÷ 6000, or 1 m³ ≈ 167 kg; confirm the current carrier quote before booking.
- A 5000 divisor is another common express planning input, but the booked service’s divisor, minimums and rounding rules control.
- Ocean LCL quotes often express a revenue-ton or W/M basis. Confirm the quote’s volume unit, weight conversion, minimums and rounding before using the common 1 CBM versus 1 metric-ton planning example.
- Compact packing can lower the quoted chargeable figure, but savings depend on the booked mode’s rule and current all-in rates.
- This is why bulky-but-light cargo “costs more than it weighs”: you pay for the room it takes, not just its mass.
What is cubic measurement (CBM)?
CBM stands for cubic metre — the volume your cargo occupies. The formula is simple:
CBM = length (m) × width (m) × height (m)
A carton measuring 120 × 80 × 100 cm is 1.2 × 0.8 × 1.0 = 0.96 CBM. Always measure the outer dimensions of the packed carton or pallet, including any overhang, because that is the space the carrier loses. CBM is the backbone of volume-based freight pricing, so getting it right is the first step to predicting cost.
How is volumetric weight calculated for air and courier?
Aircraft and vans run out of space before they run out of weight allowance, so carriers convert volume into a notional weight and bill whichever is higher.
Air-freight planning example:
Volumetric weight (kg) = L × W × H (cm) ÷ 6000
Dividing by 6000 is mathematically the same as saying 1 m³ = 166.67 kg (≈167 kg). This is a common planning conversion, not a universal rule.
Express planning example:
Volumetric weight (kg) = L × W × H (cm) ÷ 5000
Because 5000 is smaller, it produces a higher planning weight for the same box than 6000. Confirm the divisor, rounding, minimums and any per-piece method in the current carrier or service quote.
Worked example (air)
Take that 120 × 80 × 100 cm carton (0.96 CBM):
- Volume = 120 × 80 × 100 = 960,000 cm³
- Air planning weight using 6000 = 960,000 ÷ 6000 = 160 kg
- Or: 0.96 m³ × 167 ≈ 160 kg (same answer)
Under the stated 6000 assumption, an 80 kg carton would produce a 160 kg planning chargeable weight; with 5000 it would produce 192 kg. The live quote decides the actual divisor and billing rules. For a deeper walkthrough, see how to calculate chargeable weight for air and courier.
How is volume charged in ocean LCL?
Ocean LCL quotes may use a revenue-ton / W/M (weight or measurement) basis. A common planning example compares CBM with metric tonnes using 1 CBM versus 1 metric ton (1000 kg), but it is not a universal tariff rule. The quote must state its actual W/M conversion, minimum charge, rounding and any commodity or lane exception.
Worked examples (ocean LCL)
- 3 CBM weighing 600 kg. Under the stated 1-CBM/1-ton example, volume = 3 units and weight = 0.6 unit, so the planning figure is 3 revenue tons.
- 1 CBM weighing 1500 kg. Under the same example, volume = 1 unit and weight = 1.5 units, so the planning figure is 1.5 revenue tons.
These are arithmetic examples only. Confirm the actual W/M basis and minimums in the ocean quote, then compare the current all-in LCL and FCL offers for the same shipment scope; see FCL vs LCL ocean freight and container types and sizes.
How do the modes compare?
Each mode treats volume against weight differently. The table below shows the rule and the implied “break-even” density at which weight starts to win.
| Mode | Volume rule | Charged on | Volume wins when density is below |
|---|---|---|---|
| Air planning example | L×W×H (cm) ÷ 6000 | Greater of actual vs volumetric kg | ~167 kg / m³ |
| Express planning example | L×W×H (cm) ÷ 5000 | Greater of actual vs volumetric kg | ~200 kg / m³ |
| Ocean LCL planning example | Quoted W/M; example compares 1 CBM with 1 metric ton | Quoted comparison and minimums | Example break-even: ~1000 kg / m³ |
Each row is a planning model, not a promise about price. Use the live terms for each mode and compare all-in quotes for the same route, cargo, scope and deadline; no mode is inherently cheapest for every shipment.
How do I lower the chargeable figure?
Because cost follows space, packing density is the lever you control:
- Flat-pack and nest where possible. Disassembled or nested goods occupy less CBM.
- Right-size the carton. Oversized boxes with void space inflate both volumetric weight and CBM.
- Cartonise correctly. Tight, regular cartons stack and palletise efficiently and lose less space to gaps — see how to pack and palletize export cargo.
- Compare modes on the same scope. Use the packed density as an input, then compare current all-in quotes, minimums, handling and delivery for the actual route and deadline.
Frequently asked questions
How do I calculate CBM? Multiply length × width × height in metres. A 120 × 80 × 100 cm carton is 1.2 × 0.8 × 1.0 = 0.96 CBM. Use the packed outer dimensions, including any overhang on a pallet.
How many kilograms is one cubic metre in air freight? With the common planning divisor 6000, 1 m³ converts to about 166.67 kg, so 0.96 CBM is about 160 volumetric kg. Use the divisor in the current carrier quote for booking.
Why does ocean LCL use 1 CBM = 1 ton instead of a divisor? Some LCL quotes use W/M and compare CBM with metric tonnes; 1 CBM versus 1 metric ton is a common planning example. Apply it only when the quote states that conversion, and confirm minimums, rounding and exceptions.
Why is my light shipment so expensive? Because carriers bill on the space you occupy, not just mass. A box of cushions or empty plastic housings has low weight but high volume, so its volumetric weight (air/courier) or CBM (ocean LCL) sets the price.
Does the same box cost the same across modes? No. A divisor of 5000 produces more volumetric kg than 6000 for the same box, while ocean LCL uses a different basis. Calculate with the terms in each current quote before booking.
Get a quote on your actual dimensions
Cubic measurement decides which number you pay on, but the rate per kg or per CBM depends on lane, season and your exact cargo — so we never quote blind. When you are ready for real numbers, message us on WhatsApp with your origin, packed dimensions, weight and product, and we will tell you which mode wins for your shipment and send a tailored quote with a realistic transit window. For the bigger picture on choosing between modes, this is part of our guide to air and ocean freight from China.
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