It is the first number every importer needs for the landed-cost calculation — and the number most suppliers answer vaguely. Here is the real math we use when we build a container loading plan for customers.
| 20GP | ≈ 100–150 m² of standard double-glazed casement windows |
|---|---|
| 40GP | ≈ 200–240 m² |
| 40HQ | ≈ 250–300 m² |
| MOQ | 1 × 20GP — models can be mixed inside the same container |
These are planning figures for wooden-crate packing. Your exact loading plan is confirmed after the window schedule is fixed — every opening has a measured size, and the crate layout is calculated from those.
| 20GP internal | 5.90 × 2.35 × 2.39 m · 33 cbm · payload ≈ 28 t |
|---|---|
| 40GP internal | 12.03 × 2.35 × 2.39 m · 67 cbm |
| 40HQ internal | 12.03 × 2.35 × 2.69 m · 76 cbm |
The rated 33 cbm of a 20GP is a nominal number. Crated window units are rectangular, rigid and cannot be tilted past a safe angle, so real usable space is far lower — that is why the honest answer is a range, not one figure.
A common misconception is that glass weight caps the load. Run the numbers: a typical double-glazed casement window weighs 35–45 kg/m² including frame and crate share. At 150 m² that is only 6–7 tonnes — well under the 28-tonne payload of a 20GP.
What actually eats the space:
Weight only becomes the limit with triple glazing, thick laminate or large oversized units: a 300 kg single crate changes both the packing plan and the unloading equipment you need at the destination.
Rule of thumb: standard double-glazed windows are a volume problem; anything above 45 kg/m² per unit starts to be a weight problem too. Tell us your glass build and we will flag it early.
| Glass build | Triple glazing adds ~40% volume per unit → fewer m² |
|---|---|
| Unit size | Very large fixed panels waste corner space; mid-size units pack tightest |
| Window type | Fixed windows pack tighter than casements; doors are heavier and bulkier |
| Fly screens / shutters | Often shipped nested inside the window crates — nearly free space |
| Packing spec | Full crate vs. foam-only for short routes — discuss before, not after |
This is why we answer every RFQ with a container loading plan attached to the quotation — you see the crate layout before you pay the deposit, not at the port.
Villa order — 120 m²
Mixed casement and fixed units, double glazing, 24 openings. Loads as one 20GP with about 10% crate headroom to spare. One container, one deposit, 20–30 days later it sails from Tianjin.
Residential project — 3,000 m²
At 130 m² per 20GP that is roughly 23 containers. Nobody ships that in one go: we phase it by building floor, matching your site installation sequence, so cash flow and crane time both stay sane.
Opening sizes, glass build and destination port are enough to start. Within 48 hours you receive a priced quotation and a crate-by-crate container loading plan.