The question nobody thinks about carefully enough

You've got a 40ft container with four different products. Total freight bill: $3,400. How do you split it?

If you said "divide by four" — you and about 80% of importers. But that $850-each split is almost certainly wrong, and the error isn't academic. The way you allocate shared costs directly determines which products appear profitable and which appear to be bleeding money. Get it wrong, and you might discontinue a product that was actually your best performer.

The five ways to do this

Equal split

Just divide the total by the number of products. It's easy, it's fast, and it's almost never accurate. Unless every product takes the same space and weighs the same amount, someone's getting subsidised and someone's getting penalised.

By units

Every unit gets the same share. So 10,000 total units with $3,400 in freight = $0.34 each, regardless of what the product actually is.

This works okay when products are similar sizes and weights. It falls apart when you've got 500 large items and 5,000 tiny ones in the same box.

By weight

Costs split in proportion to each product's weight. Product A weighs 2,000 kg out of 5,000 total? It gets 40% of the freight cost.

This makes sense when weight is driving your cost — common with air freight and dense, heavy products. Less useful for lightweight but bulky items.

By volume

Same idea, but using cubic metres instead of kilograms. Product B takes up 10 CBM out of 22 total? It gets 45% of the freight.

For ocean freight, this is usually the most accurate method. You're paying for container space, after all. Volume is what fills the box.

By declared value

Higher-value products absorb more of the cost. This makes intuitive sense for things like insurance (you're insuring the value), but it can be weird for freight — an expensive but tiny product ends up carrying a disproportionate share of the shipping cost it barely contributed to.

So which one should you use?

Honestly, it depends on what's actually driving the cost.

Ocean freight? Volume. You're paying for space in a steel box. Allocate by CBM.

Air freight? Weight (or volumetric weight — airlines use whichever is higher). Allocate accordingly.

Insurance? Value. You're insuring against financial loss.

Customs brokerage? This is a flat fee for processing your entry. Equal split or per-unit works fine — the broker doesn't care what's in the box.

Duty and VAT? No allocation needed. These are calculated per product on their own customs values.

Let me show you why this matters

Three products, one container:

Freight: $3,400

Allocated by volume (makes sense — it's ocean freight):

• Mugs: $1,236 → $0.62/unit
• Cases: $1,545 → $0.31/unit
• Lights: $618 → $0.62/unit

Allocated by weight (for comparison):

• Mugs: $2,757 → $1.38/unit
• Cases: $184 → $0.04/unit
• Lights: $459 → $0.46/unit

Look at those phone cases — $0.31 per unit with volume versus $0.04 with weight. And the mugs swing from $0.62 to $1.38. If the mugs have a $2 margin and you're allocating by weight, they suddenly look like they're barely breaking even. Allocate by volume (which reflects reality for ocean freight), and they're comfortably profitable.

Wrong method → wrong conclusion → wrong decision.

Keep it consistent

Whatever method you choose, use the same one for every shipment of the same type. The absolute numbers matter less than being able to compare across time. If you switch methods between shipments, you'll never be able to tell whether a product is getting more or less expensive to ship — you'll just see noise.

And when a product's profitability is borderline, run it through multiple methods. If it only looks profitable under one allocation approach and terrible under the others, it's probably not as strong as you think. But if it holds up across all methods, you know the margin is real.