How to Split Shipping Costs Across Products in a Multi-SKU Shipment

Cost Allocation Methods for Importing: How to Split Shipping Costs

Cost allocation methods for importing determine how you split a single freight bill across multiple products — and the method you choose can make or break your profitability analysis. You have one 40ft container arriving from China. Inside it: 3,000 phone cases, 1,500 water bottles, 800 yoga mats, and 500 LED desk lamps. The total freight bill is $4,000.

How do you divide that $4,000 among your four products?

This is not an academic question. The method you choose directly affects the landed cost of each product, which affects your pricing decisions, which determines which products look profitable and which look like losers.

Get the allocation wrong and you might discontinue a profitable product because it appears to have thin margins — or keep pushing a loss-maker because the allocated shipping cost makes it look better than it is.

Why It Matters

Consider two extreme allocations for the phone cases in our example:

• If allocated by units: 3,000 of 5,800 total units = 51.7% of freight = $2,068 or $0.69 per case
• If allocated by volume: Phone cases take up perhaps 1.5 CBM of a 60 CBM container = 2.5% of freight = $100 or $0.03 per case

That is a $0.66 per unit difference — on a product that might sell for $11.99. The allocation method alone can swing your apparent profit margin by 5–6 percentage points.

Multiply this across your entire product range and thousands of units, and you can see why cost allocation is not something to treat casually.

5 Cost Allocation Methods for Import Shipping

Method 1: By Units (Equal Per-Unit Allocation)

How it works: Divide the total freight cost equally among all units in the shipment.

Formula: Freight per unit = Total freight ÷ Total units

This is the simplest method and the one most beginners default to.

Method 2: By Weight

How it works: Allocate freight proportionally based on each product's share of the total shipment weight.

Formula: Product freight = Total freight × (Product total weight ÷ Shipment total weight)

This method makes sense when freight is primarily determined by weight — common with air freight or when a shipment is close to the container's weight limit.

Method 3: By Volume (CBM)

How it works: Allocate freight proportionally based on each product's share of the total shipment volume in cubic metres.

Formula: Product freight = Total freight × (Product total CBM ÷ Shipment total CBM)

This is often the most logical method for ocean freight, where you are paying for container space. A product that takes up more space should bear more of the cost.

Method 4: By Value

How it works: Allocate freight proportionally based on each product's share of the total shipment value (FOB value).

Formula: Product freight = Total freight × (Product total value ÷ Shipment total value)

This method is used in some accounting frameworks and by customs authorities in certain countries. The logic is that higher-value products should absorb more freight because they can afford it.

Method 5: By Custom Ratio

How it works: You define a custom weighting based on a combination of factors — perhaps 50% by volume and 50% by weight, or a ratio that reflects your business priorities.

Formula: Varies based on your chosen weighting

This is the most flexible but also the most subjective method.

Worked Example: The Same Shipment, Five Ways

Let's use a concrete example. One 40ft container with the following products:

Total freight cost: $4,000

Results by Each Method

Method 1: By Units

Every product gets the same per-unit cost — simple but arguably unfair. A phone case weighing 80g gets the same allocation as a yoga mat weighing 1.2kg.

Method 2: By Weight

The yoga mats absorb nearly half the freight cost because they are the heaviest products by total weight.

Method 3: By Volume (CBM)

Similar to weight-based allocation, but the LED lamps take a bigger share because they are bulkier relative to their weight.

Method 4: By Value

Value-based allocation shifts costs toward the water bottles (highest total value) and away from the phone cases (lowest total value).

Method 5: Custom Ratio (50% Volume, 50% Weight)

Comparison Summary

Here is the freight cost per unit under each method, side by side:

The range for phone cases is $0.12 to $0.69 — a 5.8x difference. For yoga mats, it is $0.69 to $2.43 — a 3.5x difference. These are not rounding errors. They fundamentally change the profitability picture for each product.

How Cost Allocation Changes Product Profitability

Let's see how the choice affects apparent profitability for the yoga mats:

A 7 percentage point difference in apparent margin — just from the allocation method. If your target minimum margin is 35%, the yoga mats look viable under unit-based allocation but borderline under volume-based.

When to Use Each Method

By units — use when all products in the shipment are roughly similar in size and weight. Simple and good enough when products are homogeneous.

By weight — use when the shipment is weight-limited (close to the container's maximum weight before it is fully filled by volume). Common with dense products like metal items, ceramics, or liquids.

By volume — use when the shipment is volume-limited (the container is full by space before reaching weight limits). This is the most common scenario for consumer goods shipped by ocean freight and is generally the most defensible method.

By value — use when required by your accounting framework or customs authority. Some businesses prefer this because it ensures that low-value items do not have disproportionately high landed costs, which can make them appear unprofitable when they actually sell well.

Custom ratio — use when neither weight nor volume alone tells the full story. A 50/50 weight-volume blend is a common pragmatic choice.

The Best Cost Allocation Method for Most Importers

For most importers shipping consumer goods by ocean freight, volume-based allocation (CBM) is the most accurate and defensible method. Here is why:

1. Ocean freight is fundamentally a space-based cost — you are buying container space, not weight capacity (in most cases)
2. It reflects economic reality — a product that takes up more space in the container is genuinely using more of the resource you paid for
3. It is consistent — the same method works regardless of the product mix
4. It is auditable — volume can be calculated from product dimensions, which are objective and verifiable

However, if your shipments frequently hit weight limits before volume limits (common with heavy goods), weight-based allocation is more appropriate.

Practical Tips

Be consistent: Whatever method you choose, apply it consistently across all shipments. Switching methods between orders makes it impossible to track product profitability over time.

Document your method: Record which allocation method you use and why. If your accountant or tax authority asks how you calculated landed costs, you need to explain your methodology.

Recalculate when the product mix changes: If you add or remove products from a shipment, the allocation for every other product changes. Update your cost models accordingly.

Consider shipping products separately: If the allocation reveals that one product is disproportionately increasing freight costs for other products (e.g., bulky yoga mats driving up the total), consider whether shipping that product in its own container or via a different method would be more cost-effective overall.

Use the Import Calculator to model different allocation methods for your specific product mix. The Cost Engine supports multi-SKU shipment allocation so you can see the impact on each product's landed cost in real time.

For current container rates to use in your allocation calculations, see our shipping container cost guide for 2026. If you are deciding whether to ship all products together or separately, our FCL vs LCL cost comparison covers the break-even analysis.

Key Takeaway: Choose and Apply Your Allocation Method Consistently

There is no single "correct" way to allocate shipping costs. But choosing the wrong method — or not thinking about it at all — can distort your profitability analysis and lead to poor business decisions.

Pick a method that reflects how freight costs are actually incurred, apply it consistently, and review the impact on each product's margins. Your pricing and sourcing decisions are only as good as the cost data they are built on.