How Many Marble Slabs Fit in a 20ft Container?

The short answer

A 20-foot container fills by weight long before it fills by space. Exporters' loading guides converge on a usable load of roughly 24 to 27 tonnes, or about 470 to 500 m2 of 2 cm slabs and 285 to 312 m2 of 3 cm slabs. One exporter publishes 70 to 75 large slabs at 2 cm and 50 to 52 at 3 cm per 20-foot box; another, working from 330 x 210 cm gang-saw slabs and a 27-tonne load, gets 68 slabs at 2 cm and 45 at 3 cm; smaller slabs raise the count, not the area.

These are planning figures. The exact number depends on the stone's density, the slab format, the packing and the roads at the destination. This guide shows how to work it out for your own order.

Slab weight: the formula

Weight = area x thickness x density. Area in square metres, thickness in metres and density in kilograms per cubic metre give kilograms. A 300 x 200 cm slab is 6 m2; at 2 cm (0.02 m) and 2,850 kg/m3 it weighs 6 x 0.02 x 2,850 = 342 kg, the figure one exporter's loading table shows. A stone weight calculator built on the same method uses 2,750 kg/m3 as a mid-range granite density and 2,650 kg/m3 for marble, about 55 and 53 kg/m2 at 2 cm; a general-purpose marble calculator defaults to 2,711 kg/m3.

Density is the variable that matters most. Published ranges run 2,100 to 2,700 kg/m3 for limestone, 2,500 to 2,900 for marble and 2,600 to 3,050 for granite. Most beige Egyptian marbles such as Galala, Sunny and Katrina are dense limestones and generally sit below granites like Halayeb and Red Aswan, but the spread is real: one Egyptian exporter publishes 58 kg/m2 at 20 mm and 85 kg/m2 at 30 mm for its marble, implying a density near 2,850 kg/m3. Ask for the measured bulk density of the stone you are buying and use that rather than a generic value.

How many slabs and square metres fit

Divide the usable load by the weight per square metre for the area per container, then by the slab area for the slab count. At 27 tonnes and 2,850 kg/m3, 2 cm material comes to about 470 m2 and 3 cm to about 311 m2. An Egyptian exporter's published norms are close: about 500 m2 of 20 mm slabs or tiles, 285 to 310 m2 at 30 mm and about 800 m2 of 10 mm tiles per 20-foot container.

Two things eat into these numbers. Packing takes part of the payload: one loading guide deducts 2 to 5 percent for wooden bundles, another 3 to 10 percent for packing and stacking constraints, and A-frames and tile crates need a little more. And thinner is not simply more slabs: 1.5 cm material is more fragile, so bundles hold fewer pieces than the arithmetic suggests. One guide adds 10 to 15 percent wastage before sizing the shipment.

Payload limits: why a 40ft is not twice a 20ft

Every container carries a CSC plate stating its maximum gross mass: 30,480 kg for a standard 20-foot box, 30,480 to 34,000 kg for a standard 40-foot. Because the 40-foot container itself weighs 3,750 to 3,900 kg against 2,050 to 2,300 kg for a 20-foot, its payload is only about 15 to 20 percent higher for twice the volume. Two 20-foot containers therefore carry far more stone than one 40-foot, which is why slabs almost always ship in 20-foot units.

Since 1 July 2016 SOLAS has required the shipper to declare a verified gross mass (VGM) for every packed export container, either by weighing the loaded container on calibrated equipment or by weighing all contents including packing and dunnage and adding the container's tare. The ship's master cannot load a container without it, so packing-list weights must be measured, not nominal.

Bundles and crates versus A-frames

Slabs travel upright. The common export method is the wooden bundle: slabs stacked face to face between timber uprights, separated by plastic sheet or foam, strapped and clamped, then fastened together and blocked to the container floor. Published figures give 5 to 7 slabs per bundle, with one loading guide listing 9 to 11 at 2 cm and about 7 at 3 cm, and 6 to 8 bundles per 20-foot container; one stone seller notes a bundle can weigh up to 3.5 tonnes.

A-frames hold slabs leaning against a central ridge. The German container handbook recommends permanent steel A-frames for regular traffic and squared-lumber frames for one-off shipments: slabs are strapped to each frame half before loading, frames are blocked with timber and shored against tipping, and whether one or two frames fit a box depends on the cargo mass. A-frames unload quickly by forklift or crane but use less of the payload than bundles, so tell the supplier how you will unload.

Road weight limits at the destination

The ship accepts 28 tonnes of stone in a 20-foot box; the truck at the other end may not. US federal Interstate limits are 80,000 lb gross vehicle weight, 20,000 lb per single axle and 34,000 lb per tandem axle, and states set their own limits elsewhere. Two loading guides therefore cap a 20-foot container for US delivery at about 19,900 kg (44,000 lb) on a tri-axle chassis, and one Egyptian exporter publishes 21 tonnes for the USA against 27 for Europe. Confirm the legal payload with your freight forwarder before the supplier packs, and write it into the order.

Working it out for your order

Take the net area plus wastage, multiply by the weight per square metre for your thickness and the stone's measured density, add the packing allowance and divide by the payload your forwarder confirms. That gives the container count; the slab count follows from the format the supplier can cut. Our marble calculator runs these steps for standard thicknesses. In the enquiry, state thickness, slab or tile format, destination port and the road weight limit at delivery, and ask for a packing list with the number of bundles, the net and gross weight of each and the total for the VGM. For slab sizes and densities currently available in a particular Egyptian stone, contact us.