4 x 4 m slab at 15 cm
Concrete needed, with a 7 percent waste allowance, rounded up.
Cubic metres
2.57m³
25 kg bags
220
20 kg bags
274
cubic metres = 4 × 4 × (15 / 100) × 1.07 = 2.57 m³
In imperial, that is about 13.1 × 13.1 ft at 5.9 in, roughly 3.36 cubic yards of concrete.
Open the interactive Concrete CalculatorAbout this slab
A 4 by 4 metre slab at 15 cm is 2.4 cubic metres before waste. We add 7 percent for spillage and uneven subgrade and round up to whole bags. A 25 kg bag yields roughly 0.0117 cubic metres and a 20 kg bag about 0.0094.
Confirm the order with your supplier. Uneven subgrade, over excavation and thickened edges all add volume.
Mixing more than a few bags? A heavy duty mixing tub keeps the batch consistent and saves your back. For larger pours, price up ready mix delivery instead.
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Common questions
How much concrete for a 4x4 m slab at 15 cm?
A 4 by 4 metre slab at 15 cm thick is about 2.4 cubic metres before waste, or 2.57 cubic metres with a 7 percent allowance. That is roughly 220 bags of 25 kg mix.
Bags or ready mix for this slab?
Compare both. Bags suit small jobs, but past roughly half a cubic metre, ready mix delivered is usually cheaper and far less work than mixing by hand.
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