Freight Calculation Methodology & Planning Principles
This platform is designed to provide transparent, formula-driven planning estimates for international freight. We do not use proprietary black-box calculations or arbitrary reduction factors. This page explains every mathematical formula, standard preset, and operational limitation governing our calculators.
1. Cubic Volume (CBM & CuFt)
Open CBM Calculator →Cubic Meters (CBM, or m³) is the standard international metric unit of cargo volume in ocean shipping, air freight, and ground freight. All input dimensions (millimeters, centimeters, meters, inches, or feet) are first converted into meters before computing volume:
Cubic Feet Conversion: One cubic meter equals approximately 35.3146667 cubic feet (CuFt or CFT). When dimensions are measured in inches:
Total CBM = Total CuFt / 35.3146667
Learn more in our detailed practical guide: How to Calculate CBM & Chargeable Weight →
2. Air & Courier Dimensional Weight
Carriers charge based on cargo density because aircraft and delivery vehicles are constrained by both cubic volume and gross weight. Dimensional weight (also termed volumetric weight) converts cargo volume into a billable weight equivalent:
Important Note on Presets: Divisors vary by carrier, service tier, contract terms, and specific route tariffs. The presets offered in our calculator are common industry reference benchmarks, not universal standards:
- Air Freight Preset (6,000 cm³/kg / 166 in³/lb): A standard reference preset historically used by many IATA air carriers (equivalent to 1 CBM ≈ 167 kg). Some airlines and commercial tariffs use 5,000 cm³/kg or trade-lane-specific ratios.
- Courier Preset (5,000 cm³/kg / 139 in³/lb): A common commercial preset for international express courier services (equivalent to 1 CBM ≈ 200 kg). Domestic express or non-express services may use 4,000 or 6,000 cm³/kg.
Our calculator keeps both divisors fully user-configurable to match your specific carrier quotation.
3. Ocean Freight Weight or Measure (W/M) & Revenue Tons
Ocean Less-than-Container Load (LCL) consolidation operates under the maritime Weight or Measure (W/M) convention. Cargo is billed per Revenue Ton (RT) (also referred to as a Freight Ton), defined as the higher of cubic volume or gross weight:
where 1 Metric Tonne (MT) = 1,000 kg (2,204.62 lbs)
If a 5 CBM shipment weighs 2,000 kg (2.0 MT), it is volume-dominated and billed as 5 RT. If a 3 CBM shipment weighs 8,000 kg (8.0 MT), it is weight-dominated and billed as 8 RT.
4. Container Loading Estimation Principles
Open Container Loading →Our container loading calculator estimates the carton capacity of standard 20GP, 40GP, and 40HC containers through a rigorous 3D orthogonal grid packing algorithm:
When carton rotation is enabled, the algorithm evaluates all 6 orthogonal spatial orientations: (L, W, H), (L, H, W), (W, L, H), (W, H, L), (H, L, W), and (H, W, L).
For each orientation, grid capacity is computed by integer division:Cartons = floor(Container Length / Carton L) × floor(Container Width / Carton W) × floor(Container Height / Carton H)
Before counting capacity, the engine validates that at least one cross-section of the carton fits through the physical container door opening (width and height). Any carton whose smallest two dimensions exceed the door aperture is rejected with an explicit obstruction warning.
Carton count is capped by the container's maximum certified payload:Payload-Limited Cartons = floor(Container Max Payload / Weight per Carton)
The final capacity is strictly the minimum of geometric space capacity and payload-limited capacity.
Calculations represent orthogonal geometric packings of rigid cartons. Real-world shipping involves broken stowage (5–15% empty void space), carton bulging under compression, corrugated carton manufacturing tolerances, pallet bases and overhangs, dunnage, load securing, and legal highway axle-weight limitations. Physical pre-shipment inspection is always recommended.
5. LCL vs FCL Freight Quotation Comparison & Break-Even
Open LCL vs FCL →The LCL vs FCL calculator evaluates commercial quotation trade-offs strictly from user-entered figures:
Quotation Scope Comparability: The tool compares this calculated LCL total against entered all-in FCL container amounts (20GP, 40GP, 40HC). This comparison is only as comparable as the scope of the quotations entered. If your LCL quote includes origin CFS handling and destination document fees, your FCL quote must also include comparable origin/destination terminal handling charges (THC) and document fees for an accurate comparison.
Crossover & Break-Even Calculation: The mathematical volume tipping point where LCL cost equals an FCL quote is:
Weight-Dominated Crossover Limitation: If cargo is dense, the cargo's gross weight in metric tonnes can drive LCL costs above the FCL rate even when physical volume is small. In such cases, FCL is cheaper on a pure weight basis, even if the container is mostly empty by volume.
Read our full guide on freight trade-offs: LCL vs FCL Cost Drivers & Break-Even Guide →
6. Container Reference Specifications & Standards
View Dimensions Guide →All container dimensions, volumes, tare weights, and payload ratings in our calculators are representative reference specifications based on standard ISO 668 Series 1 freight containers:
| Container Type | Internal L × W × H (mm) | Door Opening (W × H mm) | Nominal Volume | Max Payload |
|---|---|---|---|---|
| 20' Standard (20GP) | 5,898 × 2,352 × 2,393 | 2,340 × 2,280 | 33.2 CBM | 28,200 kg |
| 40' Standard (40GP) | 12,032 × 2,352 × 2,393 | 2,340 × 2,280 | 67.7 CBM | 26,700 kg |
| 40' High Cube (40HC) | 12,032 × 2,352 × 2,698 | 2,340 × 2,585 | 76.3 CBM | 26,500 kg |
We do not claim universal exact ISO internal dimensions. While external dimensions are strictly standardized by ISO 668, internal clearances and tare weights vary between container manufacturers (CIMC, Singamas, CXIC), corrugation depths, floor material thicknesses, and individual shipping line fleets.
The actual physical CSC (Convention for Safe Containers) Safety Approval Plate mounted on the container door and individual carrier equipment records strictly control the maximum gross mass and payload for each specific container.