Slab 4 x 3 m, 10 cm thick
- Input
- 4 x 3 x 0,10 m, folga 5%
- Expected output
- 1,2 m³, 1,26 m³ com folga
Gross volume is length x width x thickness.
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concrete mix cement bags per cubic meter calculator
On the Concrete tab add the pieces with their sizes, pick the reference mix and check volume, cement bags, sand, gravel and water. It is a consumption estimate; structure requires an engineer design.
Gross volume is length x width x thickness.
1,000 ÷ 145 = 6.9 bags per m³.
8.69 bags, rounded up.
6.26 cement bags, rounded up.
July 2026 reference, indicative.
Absolute-volume calculation with typical assumptions.
Take the net wall area, multiply by the coats and divide by the coverage. A 4 x 3 m bedroom with a 2.7 m ceiling, one door (1.6 m²) and one window (2.0 m²) has 14 x 2.7 = 37.8 m² gross and 34.2 m² net. With 2 coats at 9.4 m²/L that is 7.3 L, and 8.0 L with a 10% margin. The best purchase at the example prices is two 3.6 L cans plus one 0.9 L can, or 8.1 L. The coverage printed on your own paint can always beats the default value.
The 1:2:3 is a common reference and works out to about 326 kg of cement per m³ in the tool math, but it is for budgeting, not for deciding. Slab strength depends on the structural design and site control, not only on the proportions.
The water/cement ratio sets the strength: more water makes mixing easier and weakens the concrete. That is why reference mixes carry a fixed water amount and the free mix asks for the w/c ratio, from 0.2 to 1.
Usually yes: structural design and execution are engineering activities, registered through an ART at CREA in Brazil. Confirm with the technical lead and the city hall; the tool does not replace that professional.
Floor 20 m², walls 43 m² (openings deducted: 5.6 m²)
Floor 10.5 m², walls 31.5 m² (openings deducted: 3.6 m²)
A door of 0.80 x 2.00 m is 1.6 m² and a window of 1.00 x 2.00 m is 2.0 m². Edit them to match your job. With the deduction off, the numbers are more generous.
Estimated total: R$3,789.00 across 6 items.
Estimates for budgeting. Structure (slabs, beams, columns, foundations) needs an engineer and ART.