How to Calculate CBM (Cubic Meters)
CBM stands for Cubic Meter (m³), the universal unit of volumetric measurement in international freight forwarding and ocean shipping. One cubic meter represents the volume of a cube measuring exactly one meter wide, one meter long, and one meter high (1 m × 1 m × 1 m).
To calculate CBM, measure the greatest outside dimensions of each carton or handling unit—including cardboard packaging, strapping, and pallet overhang—and apply the formula matching your measurement unit:
Metric Formulas
From Centimeters (cm):
CBM = (Length × Width × Height in cm) ÷ 1,000,000
From Millimeters (mm):
CBM = (Length × Width × Height in mm) ÷ 1,000,000,000
From Meters (m):
CBM = Length (m) × Width (m) × Height (m)
Imperial Formulas
From Inches (in):
Cubic Feet = (Length × Width × Height in in) ÷ 1,728
CBM = Cubic Feet ÷ 35.3147
Direct divisor: (L × W × H) ÷ 61,023.74
From Feet (ft):
CBM = (Length × Width × Height in ft) × 0.0283168
Worked Calculation Example:
A shipment of 50 cartons measuring 60 cm × 40 cm × 40 cm:
Volume per carton = (60 × 40 × 40) ÷ 1,000,000 = 0.096 CBM (3.39 cu ft).
Total shipment volume = 0.096 CBM × 50 cartons = 4.800 CBM (169.51 cu ft).
Ocean Shipping Container Capacities: Internal Volume vs. Practical Planning
Standard ISO intermodal shipping containers are constructed to verified structural dimensions. However, nominal internal volume does not equal practical cargo capacity. Liquid or gas could fill 100% of a container's internal cube, but solid rectangular cartons inevitably create unusable space (termed broken stowage), clearance near container doors, and void space around pallets.
| Container Type | Internal Dimensions (L × W × H) | Internal Cube (Verified) | Planning Fill Factor | Practical Planning Cube | Max Equipment Payload | US Highway Rec. (OCEMA) |
|---|---|---|---|---|---|---|
| 20ft Standard Dry (22G1) | 5.90 m × 2.35 m × 2.40 m 19.36 ft × 7.72 ft × 7.86 ft |
33.2 CBM 1,172 ft³ |
85% planning default | ~28.2 CBM ~996 ft³ |
28,130 kg 62,016 lb |
17,780 kg (39,200 lb) tandem slider chassis |
| 40ft Standard Dry (42G1) | 12.03 m × 2.35 m × 2.40 m 39.47 ft × 7.72 ft × 7.86 ft |
67.7 CBM 2,390 ft³ |
85% planning default | ~57.5 CBM ~2,032 ft³ |
28,750 kg 63,383 lb |
19,960 kg (44,000 lb) tandem gooseneck |
| 40ft High Cube (45G1) | 12.03 m × 2.35 m × 2.70 m 39.47 ft × 7.71 ft × 8.86 ft |
76.3 CBM 2,694 ft³ |
88% planning default | ~67.1 CBM ~2,371 ft³ |
28,600 kg 63,052 lb |
19,820 kg (43,700 lb) tandem gooseneck |
Critical Planning Notice on Fill Factors & Practical Fit:
Volume utilization is a planning estimate and does not guarantee physical carton fit. FreeLoadPlan uses 85% (and 88% for high cube) as software planning baseline defaults to help shippers estimate container count. These fill factors are NOT an official ISO or industry standard. Actual loadability depends on package geometry, orientation constraints, pallet bases, ceiling clearance, and dunnage.
Furthermore, container transport in the United States is governed by the Federal Bridge Formula (23 CFR § 658.17) and state axle weight caps (80,000 lb gross vehicle weight). Ocean Carrier Equipment Management Association (OCEMA) guidelines recommend restricting 20ft container cargo weight to approximately 39,200 lb (17,780 kg) on standard tandem slider chassis to prevent highway axle overload.
Ocean LCL (Less-Than-Container-Load) Weight or Measure (W/M)
When shipping cargo that does not fill an entire ocean container, forwarders consolidate multiple shippers' cargo into shared containers. This service is termed LCL (Less-Than-Container-Load).
Ocean freight rates for LCL are assessed based on Weight or Measure (W/M), also referred to as the Revenue Ton (RT) or Freight Ton (FT):
Ocean LCL Revenue Ton Rule:
1 Revenue Ton (RT) = Maximum of [ Volume in CBM , Weight in Metric Tons ]
Standard baseline: 1 CBM is equivalent to 1,000 kg (1.0 Metric Ton). Whichever number is greater governs the billable freight calculation.
Shipment volume: 6.0 CBM
Gross cargo weight: 1,800 kg (1.8 Metric Tons)
Comparison: 6.0 CBM > 1.8 MT
Billable: 6.0 Revenue Tons (RT)
The cargo is light and bulky (density < 1,000 kg/m³). Freight is charged on volume.
Shipment volume: 2.0 CBM
Gross cargo weight: 4,500 kg (4.5 Metric Tons)
Comparison: 4.5 MT > 2.0 CBM
Billable: 4.5 Revenue Tons (RT)
The cargo is dense and heavy (density > 1,000 kg/m³). Freight is charged on gross weight.
Important Forwarding Note: Revenue ton calculation represents basic freight assessment. LCL invoices also include forwarder origin/destination terminal handling charges (THC), documentation fees, currency adjustment factors (CAF), and minimum billing thresholds (tariff-specific minimums).
Air Cargo Volumetric Weight vs. Ocean CBM
Aircraft capacity is limited by both maximum takeoff weight and cargo hold volume. To compensate for light, bulky shipments taking up aircraft space, the International Air Transport Association (IATA) establishes standard volumetric weight rules under Cargo Services Conference (CSC) Resolution 502:
IATA Volumetric Weight Standard (Resolution 502):
Metric: Volumetric Weight (kg) = (Length × Width × Height in cm) ÷ 6,000
Equivalence: 1 CBM = 166.67 kg volumetric weight
Imperial: (Length × Width × Height in in) ÷ 166 = Volumetric Weight (lb)
The airline compares the actual scale weight against the volumetric weight and bills whichever is higher (termed Chargeable Weight).
| Freight Mode | Volumetric Ratio | Equivalent 1 CBM Weight (before carrier rounding) | Governing Framework |
|---|---|---|---|
| Ocean LCL (Freight Ton) | 1,000 kg / m³ | 1,000 kg (1.0 MT) | Carrier LCL tariffs (e.g. Maersk LCL terms) |
| IATA Air Cargo | 6,000 cm³ / kg | 166.67 kg | IATA CSC Resolution 502 |
| Courier Express Parcel (Intl / Daily Rates) | 5,000 cm³ / kg (divisor 139) | 200 kg (metric); ~199.14 kg (imperial) | Carrier terms (FedEx / UPS Daily / DHL Express) |
| US Domestic Courier Parcel (Retail Rates) | divisor 166 (in³ / lb) | 166.75 kg | UPS Retail Service Guide (divisor 166) |
Verified Standards & Freight Reference Sources
All container dimensions, structural ratings, and volumetric baselines in this tool are sourced from official carrier fleet guides and published international freight conventions:
| Standard / Organization | Scope | Official Citation & Link | Reviewed Date |
|---|---|---|---|
| Hapag-Lloyd AG | 20ft, 40ft, and 40ft High Cube container fleet specifications | Hapag-Lloyd Container Fleet (opens in new window) | 2026-09-17 |
| OCEMA / Maersk | Recommended maximum gross allowable cargo weights under US bridge laws | OCEMA Highway Guidelines (opens in new window) | 2026-09-17 |
| A.P. Moller - Maersk | Less-Than-Container-Load (LCL) freight terms and Revenue Ton (RT) rules | Maersk LCL Conditions (opens in new window) | 2026-09-17 |
| IATA (Resolution 502) | Air Cargo Services Conference Resolution 502 volumetric weight calculation | IATA CSC Resolution 502 (opens in new window) | 2026-09-17 |