Comparing the Sensitivities of Different Transport Modes – Air Freight, Ocean Freight, and Express Delivery: Which is Most Afraid of Bulk Cargo?

In logistics, “bulky cargo” (also known as light cargo or bulky cargo) is a major headache for logistics managers and shippers. It refers to cargo that is very light but large in volume. The criterion for determining bulk cargo is typically the cargo’s density, which is the ratio of its actual weight to its volumetric weight.

The commonly used formula for calculating volumetric weight in the transportation industry is: Volumetric Weight (kg) = Length (cm) × Width (cm) × Height (cm) / Conversion Factor. This factor varies by transport mode and is key to understanding its sensitivity.

Of all transport modes, air freight is the most sensitive to bulk cargo and is the most “afraid” of it. Express delivery comes in second, while ocean freight is the least sensitive.

Let’s take a detailed look at why these three modes are afraid of bulk cargo and the varying degrees of their fear.

1. Air Freight: Most Feared by Bulk Cargo, Most Stringent Billing Rules
   Sensitivity: ★★★★★ (Highest)

Core Reason: Space is an extremely scarce and expensive resource.

Billing Rules: The air freight conversion factor is typically 6000 (or 167, meaning 1 cubic meter = 167 kg). This means:

Volumetric Weight (kg) = Length × Width × Height (cm) / 6000

If the actual weight of the cargo is less than this calculated volumetric weight, it will be charged based on the volumetric weight.

Why Feared:

Aircraft space is extremely valuable: Aircraft capacity and cabin space are strictly limited. An aircraft’s revenue depends on how much weight it can carry for a fee. A large but lightweight box takes up space that could otherwise be used for higher-value, heavier cargo, resulting in a sharp drop in airline revenue.

High Operating Costs: Fuel, airport landing fees, and labor costs are extremely expensive. Transporting bulk cargo means delivering less “effective weight” for the same cost, resulting in very low unit revenue.

Significant Billing Variations: For bulk cargo, the final air freight bill can be exorbitant, calculated based on volumetric weight, far exceeding the price calculated based on actual weight, leaving shippers feeling the pinch.

Conclusion: Air freight charges based on whichever is more valuable, “weight” or “volume.” However, bulk cargo highlights the “worthlessness” of volume, making air freight the most sensitive.

II. International Express (e.g., DHL, FedEx, UPS): Equally sensitive, with similar rules.
Sensitivity: ★★★★☆ (Very High)

Core Reason: Similar in nature to air freight, but with a more complex network.

Billing Rules: International express delivery typically uses a stricter conversion factor of 5000 (i.e., 1 cubic meter = 200 kg).

Volumetric Weight (kg) = Length × Width × Height (cm) / 5000

This factor is larger than for air freight, meaning that a box of the same size will have a higher calculated volumetric weight and higher charges for express delivery.

Why it’s so scary:

Based on the air freight network: International express delivery relies primarily on the aviation network for trunk routes, inheriting all of air freight’s characteristics of being sensitive to cargo space.

High end-of-line processing costs: Express deliveries must undergo sorting, scanning, and loading and unloading at multiple transfer stations. A large bulky shipment takes up space on conveyor belts and sorting grids, reducing overall system efficiency and increasing manual handling complexity, thereby driving up operating costs.

“Last-mile” delivery challenges: A large box may only fit on one electric tricycle, severely impacting delivery efficiency – something express delivery companies are extremely reluctant to see.

Conclusion: International express delivery is just as sensitive to bulky shipments as air freight, and in some cases, even more so due to the complexity of end-of-line operations.

3. Ocean Freight: Least Afraid of Bulk Cargo, But Not Insensitive
   Sensitivity: ★☆☆☆☆ (Lowest)

Core Reason: Relatively abundant space resources and different billing models.

Billing Rules: Ocean freight primarily uses two models:

Full Container Load (FCL): Charges are based on the entire container, not weight or volume. As long as your bulk cargo fits within the container and falls within the weight limit (shipping companies have weight restrictions), the cost is fixed. Bulk cargo is virtually invisible here.

Less than Container Load (LCL): Charges are based on volume, typically 1 cubic meter = 1 ton. The conversion factor is 1,000,000 (cm³) / 1,000 (kg) = 1,000. This factor is significantly higher than the 5,000/6,000 for air freight and express delivery.

Freight = Unit Rate (e.g., USD/RT) × Volume (m³)

This means that for bulk cargo, LCL ocean freight also charges by volume, but the calculation standard (1 CBM: 1000 kg) is much more tolerant of bulk cargo. Only extremely light bulk cargo with a density less than 1000 kg/m³ (equivalent to the density of water) will suffer a significant disadvantage.

Why it’s least worrying:

Large ship capacity: Container ships have very large cargo capacity and deadweight, so the impact of a single bulk cargo on overall operational efficiency is minimal.

Different cost structures: Variable costs (such as fuel) in ocean freight account for a smaller proportion than fixed ship depreciation and personnel costs, so the marginal cost increase of loading an additional bulk cargo is not significant.

Conclusion: Ocean freight considers both weight and volume, but tends to favor “as much as can be loaded.” In FCL freight, the issue of bulk cargo is completely ignored; in LCL freight, the billing rules are much more lenient towards bulk cargo than in air freight.

Comparison Summary
Transportation Method, Fear of Bulk Cargo, Common Conversion Factors, Core of the Billing Rules, Root Causes
Air Freight ★★★★★ (Most Feared) 1:6000 Charged based on the greater of actual weight and volumetric weight. Space is an extremely expensive and scarce resource.
International Express ★★★★☆ (Very Feared) 1:5000 Charged based on the greater of actual weight and volumetric weight. Reliance on air transport, and end-of-line operational efficiency is crucial.
Ocean Freight (LCL) ★☆☆☆☆ (Least Feared) 1:1000 Charged based on volume (1 CBM ≈ 1000 kg). Huge shipping capacity, relatively abundant space.
Ocean Freight (FCL) ☆☆☆☆☆ (Not Feared) Not Applicable Charged based on the entire container. The shipper has purchased the right to use a fixed space.
Advice for Shippers
Calculate Before Shipping: Before choosing a shipping method, always calculate and compare the volumetric weight and actual weight of your shipment.

Optimize Packaging: For bulky goods, optimizing packaging design (such as vacuuming, collapsing, and eliminating unnecessary fillers) to minimize volume is the most effective way to reduce costs.

Choose the Right Shipping Method:

For high-value, urgently needed bulky goods, air freight or express delivery may be the only option.

For low-value, less urgent bulky goods, ocean freight is undoubtedly the best option, especially when combined shipping (LCL) or full container loads are possible.

Consult a professional: Freight forwarders can provide the optimal packaging and shipping solution based on the specific circumstances of your shipment, helping you find the optimal balance between timeliness and cost.

In short, air freight and express delivery prioritize space and therefore impose heavy taxes on bulky goods that take up space. Ocean freight, on the other hand, practices space sharing and is naturally much more tolerant of bulky goods.