Case Comparison: Billing Differences for the Same Goods in Sea Freight and Air Freight

In the international logistics system, sea freight and air freight have developed distinctly different billing logics due to inherent differences in carrier characteristics, cost structures, and capacity constraints—sea freight centers on the principle of “charging by the larger one between weight ton and measurement ton”, while air freight follows the “volumetric weight-dominated” rule. This difference is not merely abstract regulatory text but is directly reflected in the freight calculation results for the same goods: for an identical batch of goods, sea freight may charge based on volume, while air freight costs could soar several times due to high space costs; conversely, dense cargo may be constrained by weight in sea freight but have controllable costs in air freight due to its small volume proportion. Through three typical cases of light cargo, dense cargo, and special goods, this article systematically compares the full-process billing differences for the same goods in sea and air freight, analyzes the root causes of these differences, and refines targeted strategies for selecting transportation modes.

I. Case Foundation: Common Parameters and Scenario Settings for Three Types of Typical Goods

To ensure the objectivity of the comparison, three types of goods covering different densities and categories are selected as research objects. The basic parameters of the goods, place of departure, and destination are uniformly set, with only the transportation mode changed for billing calculations.

(1) Common Scenario Settings

• Place of Departure: Shanghai, China (Port/Airport)
• Destination: Hamburg, Germany (Port/Airport)
• Calculation Period: Off-peak season (to avoid interference from temporary surcharges)
• Basic Rates (Market Average):
• Sea Freight (LCL): 120 USD/weight ton/measurement ton
• Air Freight (General Cargo): 18 USD/kg (billing weight)
• Surcharges: Sea freight includes a 15% fuel surcharge; air freight includes a 20% fuel surcharge

(2) Basic Parameters of Three Types of Goods

II. Case 1: Light Cargo (Plush Toys) – Air Freight Dominated by Volumetric Weight, Sea Freight by Measurement Ton

The core characteristic of light cargo is “density below the billing threshold” (sea freight < 1 ton/cubic meter, air freight < 167kg/cubic meter). Its billing differences are mainly reflected in the dominance of volumetric weight/measurement ton on freight costs and the transmission effect of space costs under different transportation modes.

(1) Full Sea Freight Billing Process (LCL)

1. Core Parameter Calculation

• Measurement Ton Calculation: Total net volume = 6 cubic meters (no packaging protrusions, calculated directly by net volume). Sea freight measurement ton = 6 (1 cubic meter = 1 measurement ton).
• Weight Ton Calculation: Total actual weight = 800kg = 0.8 weight ton.
• Billing Weight Determination: Measurement ton (6) > Weight ton (0.8), so billing is based on 6 measurement tons.

2. Freight Composition Calculation

• Basic Freight: 6 × 120 = 720 USD
• Fuel Surcharge: 720 × 15% = 108 USD
• Total Freight: 720 + 108 = 828 USD
• Unit Weight Freight: 828 ÷ 0.8 = 1035 USD/ton

(2) Full Air Freight Billing Process (General Cargo)

1. Core Parameter Calculation

• Volumetric Weight Calculation: Per IATA 6000 coefficient, total net volume = 6 cubic meters = 6,000,000 cubic centimeters. Volumetric weight = 6,000,000 ÷ 6000 = 1000kg.
• Actual Weight Calculation: 800kg
• Billing Weight Determination: Volumetric weight (1000) > Actual weight (800), so billing is based on 1000kg.

2. Freight Composition Calculation

• Basic Freight: 1000 × 18 = 18,000 USD
• Fuel Surcharge: 18,000 × 20% = 3600 USD
• Total Freight: 18,000 + 3600 = 21,600 USD
• Unit Weight Freight: 21,600 ÷ 0.8 = 27,000 USD/ton

(3) Core Comparison of Billing Differences

(4) Analysis of Root Causes for Differences

1. Difference in Space Cost Transmission: The unit space cost of sea freight is approximately 12-15 USD/cubic meter, so the space cost for 6 cubic meters is only 72-90 USD; the unit space cost of air freight is about 3000-3500 USD/cubic meter, leading to a space cost of 18,000-21,000 USD for 6 cubic meters, directly resulting in a 25-fold gap in basic freight.
2. Difference in Billing Threshold Adaptation: The density of plush toys is 133kg/cubic meter, below the 167kg/cubic meter threshold for air freight, requiring billing by volumetric weight. Although higher than the 0.8 weight ton for sea freight, the cost increment corresponding to the difference between measurement ton and weight ton (5.2) in sea freight is only 624 USD, far lower than the 3600 USD increment corresponding to the difference between volumetric weight and actual weight (200kg) in air freight.

III. Case 2: Dense Cargo (Hardware Accessories) – Sea Freight Dominated by Weight Ton, Air Freight with Controllable Actual Weight

The core characteristic of dense cargo is “density above the billing threshold” (sea freight > 1 ton/cubic meter, air freight > 167kg/cubic meter). Its billing differences are mainly reflected in the strictness of weight constraints and the impact of volume proportion on transportation mode selection.

(1) Full Sea Freight Billing Process (LCL)

1. Core Parameter Calculation

• Measurement Ton Calculation: Total net volume = 0.45 cubic meters, measurement ton = 0.45.
• Weight Ton Calculation: Total actual weight = 4000kg = 4 weight tons.
• Billing Weight Determination: Weight ton (4) > Measurement ton (0.45), so billing is based on 4 weight tons.

2. Freight Composition Calculation

• Basic Freight: 4 × 120 = 480 USD
• Fuel Surcharge: 480 × 15% = 72 USD
• Total Freight: 480 + 72 = 552 USD
• Unit Weight Freight: 552 ÷ 4 = 138 USD/ton

(2) Full Air Freight Billing Process (General Cargo)

1. Core Parameter Calculation

• Volumetric Weight Calculation: Total net volume = 0.45 cubic meters = 450,000 cubic centimeters. Volumetric weight = 450,000 ÷ 6000 = 75kg.
• Actual Weight Calculation: 4000kg
• Billing Weight Determination: Actual weight (4000) > Volumetric weight (75), so billing is based on 4000kg.

2. Freight Composition Calculation

• Basic Freight: 4000 × 18 = 72,000 USD
• Fuel Surcharge: 72,000 × 20% = 14,400 USD
• Total Freight: 72,000 + 14,400 = 86,400 USD
• Unit Weight Freight: 86,400 ÷ 4 = 21,600 USD/ton

(3) Core Comparison of Billing Differences

(4) Analysis of Root Causes for Differences

1. Difference in Weight Cost Structure: The unit weight carrying cost of sea freight carriers (containers) is approximately 30-40 USD/ton, so the weight cost for 4 tons is only 120-160 USD; the unit weight carrying cost of air freight carriers is about 18,000-20,000 USD/ton, leading to a weight cost of 72,000-80,000 USD for 4 tons. The cost gap stems from rigid costs such as fuel consumption and load restrictions in air freight.
2. Neutral Impact of Volume Proportion: Dense cargo has an extremely small volume proportion (0.45 cubic meters), which does not trigger volumetric weight/measurement ton-dominated billing in either transportation mode. The billing difference is entirely determined by the unit cost of weight, so the air freight cost for dense cargo is always far higher than that of sea freight.

IV. Case 3: Special Goods (Live Pets) – Differences Dominated by Surcharges, Costs Determined by Rule Adaptation

Billing differences for special goods (live animals, dangerous goods, etc.) are not only reflected in basic freight but also stem from different pricing rules for special needs under the two transportation modes—sea freight has fewer special clauses, while air freight has complex surcharges due to strict transportation requirements.

(1) Full Sea Freight Billing Process (Special Cargo LCL)

1. Core Parameter Calculation

• Measurement Ton Calculation: Total net volume = 2.4 cubic meters (pet crates include ventilation gaps, calculated by actual packaging volume), measurement ton = 2.4.
• Weight Ton Calculation: Total actual weight = 300kg = 0.3 weight ton.
• Billing Weight Determination: Measurement ton (2.4) > Weight ton (0.3), so billing is based on 2.4 measurement tons.

2. Freight Composition Calculation (Including Special Surcharges)

• Basic Freight: 2.4 × 120 = 288 USD
• Fuel Surcharge: 288 × 15% = 43.2 USD
• Special Surcharges: Live cargo quarantine fee 200 USD/per shipment, ventilated cabin fee 100 USD
• Total Freight: 288 + 43.2 + 200 + 100 = 631.2 USD
• Unit Weight Freight: 631.2 ÷ 0.3 = 2104 USD/ton

(2) Full Air Freight Billing Process (Live Cargo)

1. Core Parameter Calculation (Including Special Rule Adaptation)

• Volumetric Weight Calculation: Live animals require 20% additional space for movement. Billing volume = 2.4 × 1.2 = 2.88 cubic meters = 2,880,000 cubic centimeters. Volumetric weight = 2,880,000 ÷ 6000 = 480kg.
• Actual Weight Calculation: 300kg (including pet crate weight)
• Billing Weight Determination: Volumetric weight (480) > Actual weight (300), so billing is based on 480kg.

2. Freight Composition Calculation (Including Special Surcharges)

• Basic Freight: 480 × 18 = 8640 USD
• Fuel Surcharge: 8640 × 20% = 1728 USD
• Special Surcharges: Live animal quarantine fee 300 USD/per shipment, temperature-controlled cabin fee 800 USD, escort service fee 500 USD
• Total Freight: 8640 + 1728 + 300 + 800 + 500 = 11,968 USD
• Unit Weight Freight: 11,968 ÷ 0.3 ≈ 39,893 USD/ton

(3) Core Comparison of Billing Differences

(4) Analysis of Root Causes for Differences

1. Pricing Difference for Special Services: Air freight has far higher service requirements for live cargo than sea freight—needing temperature control (±2℃), real-time monitoring, and professional escort. The unit cost of these services is 5-8 times that of ventilated cabins in sea freight. In contrast, sea freight only requires basic ventilation and quarantine declaration, with surcharges accounting for only 47.5% (300/631.2) of total freight, while air freight surcharges account for 13.3% (1600/11,968) but have an absolute gap of 1300 USD.
2. Difference in Special Rules for Volume Calculation: Air freight mandates 20% additional space for live cargo, increasing volumetric weight from 400kg (original volume 2.4 cubic meters) to 480kg and raising basic freight by 1440 USD. Sea freight has no such rule, with measurement tons calculated directly by actual packaging volume without additional costs.

V. Common Difference Rules Across Three Cases and Transportation Mode Selection Strategies

The above case comparisons show that billing differences for the same goods in sea and air freight are not random but are jointly determined by three core factors: “density adaptability”, “cost structure”, and “rule constraints”. Based on this, targeted transportation mode selection strategies can be refined.

(1) Summary of Common Difference Rules

1. Cost Magnitude Difference: Air freight is always more expensive than sea freight, with a relatively smaller gap for light cargo.

The total air freight cost for the three types of goods is more than 18 times that of sea freight. However, the gap for light cargo (26.1x) is smaller than that for dense cargo (156.5x). The core reason is that air freight costs for light cargo are dominated by space, while sea freight has low space costs but a large difference between measurement ton and weight ton; air freight costs for dense cargo are