The landed-cost math behind small China wholesale orders (and a 30-line calculator)

PickByU — Fri, 13 Nov 2026 13:15:45 +0000

A supplier quotes $5.31 a unit at 96 pieces. Freight is "around $90, maybe a bit more". The buyer opens a spreadsheet, multiplies, adds the freight estimate, and marks up against that number.

Then the carton arrives: the freight invoice is bigger than quoted because the line billed volumetric weight, duty is assessed on goods plus freight, and that little handoff fee between the warehouse and the carrier was never in the sheet. The product was exactly as ordered. The unit cost landed 38% higher than planned.

This is not a supplier problem. It is a modelling problem, and it shows up in almost every small import because the numbers that decide the order are not the numbers in the supplier's quote.

Here are the four that actually matter, and the code that sanity-checks them before an order goes out.

1. Chargeable weight is not the weight on the scale

Every air and express line prices the greater of two numbers:

actual weight — what the parcel weighs;
volumetric weight — the space it occupies, divided by a constant.

The constant is set by the line, not by physics. 5000 cm³/kg and 6000 cm³/kg are the two you will meet most often. The smaller the divisor, the more you pay for air in a box.

So a carton of light goods — textiles, plush, empty packaging, anything that ships "fluffy" — pays for its air, not its mass. A 55 × 40 × 35 cm carton at a 5000 divisor is 15.4 kg chargeable even if the scale says 12.1 kg. With sea freight the divisor and the rate are different, but the principle is identical.

2. Duty is assessed on more than the goods

Most destinations assess import duty on the customs value, and depending on the destination that value can include freight and insurance, not just the item price. A 12% duty on goods alone and a 12% duty on goods plus freight are different orders when freight is 20% of the total.

This is also where "cheap per unit" quotes quietly fall apart: a low unit price with a big carton can land higher than a slightly more expensive item that packs tight.

3. Fixed cost is per shipment, not per unit

Every shipment carries costs that do not scale with its contents: a minimum charge, a handling step, a document fee, an inspection, a repack. Split an order into eight parcels and you pay eight times, and you also multiply the chance that one parcel goes missing or arrives a week late while the other seven sit in a warehouse.

4. The unit cost you should be tracking

Put those inputs together and the formula is short:

// Illustrative rates — replace with your own live quote.
const rates = {
  freightPerKg: 6.8,   // USD/kg, air express example
  divisor: 5000,       // cm³ per kg, set by the line
  dutyRate: 0.12,      // depends on HS code + destination
  perShipmentFee: 15,  // minimum charge / handling, example
};

function landedCost({ qty, unitPrice, actualKg, dims }, r = rates) {
  const volumetricKg = (dims[0] * dims[1] * dims[2]) / r.divisor;
  const chargeableKg = Math.max(actualKg, volumetricKg);
  const goods = qty * unitPrice;
  const freight = chargeableKg * r.freightPerKg;
  const duty = (goods + freight) * r.dutyRate;
  const total = goods + freight + duty + r.perShipmentFee;

  return {
    volumetricKg: +volumetricKg.toFixed(2),
    chargeableKg: +chargeableKg.toFixed(2),
    goods: +goods.toFixed(2),
    freight: +freight.toFixed(2),
    duty: +duty.toFixed(2),
    total: +total.toFixed(2),
    perUnit: +(total / qty).toFixed(2),
  };
}

Run it on a realistic small order — 8 styles × 12 pieces, $510 of goods, one 55 × 40 × 35 cm carton, 12.1 kg on the scale:

volumetricKg 15.40 · chargeableKg 15.40
goods 510.00 · freight 104.72 · duty 73.77 · fee 15.00
total 703.49 · perUnit 7.33   (goods-only per unit: 5.31)

The markup you planned against $5.31 has to cover $7.33. That is the gap that eats a small order, and it is almost never in the supplier's quote.

The split-shipment trap

The same function answers the obvious follow-up question: is it cheaper to ship each style separately, straight from each supplier?

function shippingCost(parcels, { freightPerKg, divisor, perShipmentFee }) {
  return parcels.reduce((sum, p) => {
    const vol = (p.dims[0] * p.dims[1] * p.dims[2]) / divisor;
    return sum + Math.max(p.actualKg, vol) * freightPerKg + perShipmentFee;
  }, 0);
}

Eight small parcels of 30 × 22 × 18 cm and 1.8 kg each, at the same illustrative rates:

8 parcels, shipped separately : 129.25 freight + 120.00 fees = 249.25
1 merged carton 55×40×35 cm    : 104.72 freight +  15.00 fees = 119.72

Same goods, $130 difference, and the merged carton is one tracking number instead of eight. The exact numbers depend entirely on the rates you plug in — that is the point of writing it as a function — but the shape is always the same: fixed cost multiplies by parcel count, and empty space multiplies by divisor.

What makes consolidation actually work

Physically merging parcels is easy. Doing it without losing track of anything is the hard part, and it comes down to one boring decision: every inbound parcel gets a record before it goes on a shelf.

{
  "parcel_id": "PBU-2026-000123",
  "supplier_ref": "s-8842",
  "carrier_tracking": "…",
  "received_at": "2026-11-13T09:12:00+08:00",
  "qty": 12,
  "actual_kg": 1.8,
  "dims_cm": [30, 22, 18],
  "photos": ["label", "opened", "contents"],
  "declared_value_usd": 63.75
}

With that row you can, months later, answer the questions that otherwise become arguments: which supplier shorted you three pieces, what the carton weighed before it was repacked, whether the box was damaged on arrival or in transit, and what the real chargeable weight was when the freight was quoted. Without it, every dispute is your word against a tracking screen.

Two rules make the schema work:

Measure at check-in, not at shipping. Dimensions taken after repacking tell you nothing about what the supplier sent.
Photograph the label and the opened contents. The label links the parcel to the supplier; the contents link it to the shortage claim.

If you are buying from several suppliers and holding stock before a single outbound shipment, this record is also your inventory ledger. Weight and dimensions are the only inputs to the freight quote, so capturing them once, at the point of receipt, saves you from re-measuring a carton you have already taped shut.

What PickByU does about it

PickByU is a China sourcing and shipping service built around this exact workflow for small wholesale orders: no container minimum, mixed SKUs, and one consolidated shipment instead of a pile of small parcels.

Concretely, the parts that map to the math above:

You search a curated catalog or live supplier listings reaching 100M+ products, and pay in USD from a wallet; the buying is done on your instruction.
Every inbound parcel is counted, weighed, measured and photographed at the China warehouse, and stored free for 90 days — long enough to collect several suppliers' goods before deciding what ships.
Parcels bought elsewhere can be sent to the same warehouse and merged with PickByU purchases into one carton.
Air, express and sea quotes are live at packing time, and delivery is tracked door to door to 200+ destinations.

Import duties and taxes are the buyer's responsibility, and freight is billed after packing at the carrier rate — which is why the calculation above starts with the packed carton and not with an estimate.

Five rules that survive any rate card

Quote the carton, not the unit. Ask for packed dimensions and weight for the quantity you are actually buying.
Divide before you compare. Two suppliers quoting the same unit price are not comparable until the packed volume is in the number.
Count the fixed costs. Minimum charges and handling fees are per shipment; they punish splitting.
Hold before you ship. A 90-day window turns eight small purchases into one decision about what is worth sending.
Record every parcel on arrival. Weight, dimensions, photos, and a declared value. It is your only evidence later.

The supplier's per-unit price is the first number in the calculation. It is rarely the one that decides whether the order works.

Disclosure: this post was prepared for PickByU, the service linked above. The calculator is plain JavaScript and the example rates are illustrative, not a quote — swap in your own line's rates before you trust any number it prints.

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