Freight per unit is usually the difference between a 28% and a 34% landed margin, and freight per unit is decided by one number most buyers never ask for: units per container. This page gives you the math to check any supplier's claim in two minutes.
Start from usable volume, not nominal volume
| Container | Internal dims (m) | Nominal CBM | Usable CBM | Payload |
|---|---|---|---|---|
| 20GP | 5.90 × 2.35 × 2.39 | 33 | ≈28 | ≈28 t |
| 40GP | 12.03 × 2.35 × 2.39 | 67 | ≈58 | ≈26 t |
| 40HQ | 12.03 × 2.35 × 2.69 | 76 | ≈65–68 | ≈26 t |
The gap between nominal and usable is carton void, door clearance, and the fact that nothing stacks perfectly. Planning on the nominal number is how people book a container that arrives 15% short.
The formula, with real numbers
units per container = usable CBM ÷ (carton CBM ÷ packing efficiency)
Packing efficiency is the number that separates a supplier who has actually loaded this product from one who is guessing. Typical values:
| Product | Carton CBM | Packing efficiency | Units per 40HQ (≈66 usable CBM) |
|---|---|---|---|
| Armless upholstered dining chair | 0.075 | 88% | ≈770 |
| Dining chair with arms | 0.110 | 85% | ≈510 |
| Stackable banquet chair (stack of 4) | 0.230 / stack | 92% | ≈2,100 pcs |
| Bar stool, fixed height | 0.095 | 85% | ≈590 |
| Bar stool, gas-lift swivel | 0.130 | 78% | ≈395 |
| 3-seat sofa, conventional | 1.60 | 75% | ≈31 (volume-bound) |
| 3-seat sofa, roll-packed | 0.65 | 85% | ≈86 |
Where the numbers go wrong
1. Stackability assumed, not tested
A chair designed to stack usually ships as a stack of 4 with a cap and a strap. A chair that merely "looks stackable" ships individually, and the loading quantity drops by half. Ask for a loading photo from a previous shipment — a supplier who has shipped the product has one.
2. Carton size measured before the last design change
An armrest added 2 cm to the width changes the nesting and can cost 60 chairs per container. The carton dimension must be measured on the production carton, not estimated from the drawing.
3. Roll-pack claimed without a rebound figure
Compression is only a saving if the foam recovers. High-resilience moulded foam at 32–45 kg/m³ with a recorded 72-hour rebound is a real 55–60% volume reduction. Low-density foam compressed for six weeks comes out soft and stays soft — you saved freight and destroyed the product. How we test it →
4. Weight limit ignored on dense products
Chairs and upholstery are volume-bound, not weight-bound: a 40HQ of dining chairs is typically 8–14 t against a 26 t allowance. Stone-topped tables and compact metal bases are the exceptions — there, you hit weight first and pay for air.
Mixed loads: the rule that saves the most money
Most first orders are not one SKU. The rule that keeps a mixed container efficient is fill by volume, split by weight: load the dense items low and forward, the light bulky items high and aft, and never let one SKU's carton shape create a chimney of air. A well-planned mixed 40HQ of chairs, stools and sofas reaches 85–90% volume utilisation; a badly planned one reaches 70%, and you have paid for the difference.
What this does to your landed cost
At USD 2,400 per 40HQ, 770 chairs carry USD 3.12 of freight each. At 510 chairs, the same container carries USD 4.71. That USD 1.59 difference on a USD 25 FOB chair is 6% of the landed cost — larger than most of the price negotiations buyers spend weeks on.
Which is the practical conclusion: negotiate the loading quantity before you negotiate the price. Run the numbers per container →
Get the loading count on your own SKU
Send a photo or dimensions. You get the carton CBM, units per 20GP and 40HQ, and the freight per unit at your port — plus FOB China and Vietnam side by side.
Request a quote → Build a quote sheet →Related
Importing furniture from China to Germany · FOB vs DDP · Dining chairs · Bar and counter stools · Modular sofas