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What are you pouring?
Strength
Slabs, most house work. Area = length × width.Concrete
2.16
m³ incl. 8%
Cement
16
bags, 50 kg
Stone
1.5
m³, 19 mm
- Before waste
- 2 m³
- Concrete sand
- 1.5 m³ (needs 1.4)
- Stone, 19 mm
- 1.5 m³ (needs 1.4)
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How it’s worked out
- Volume = 20 m² × 0.1 m = 2 m³
- With waste = 2 × 1.08 = 2.16 m³
- Cement = 2.16 × 7 bags = 15.1, rounded up to 16 bags
- Sand = 2.16 × 0.65 = 1.4 m³, ordered as 1.5 m³
- Stone = 2.16 × 0.65 = 1.4 m³, ordered as 1.5 m³
Assumptions
- A 25 MPa site mix, per m³ of concrete: 7 bags of cement, 0.65 m³ concrete sand, 0.65 m³ of 19 mm stone.
- Sand and stone are loose volumes, the way suppliers sell them, ordered in half cubes (0.5 m³).
- Cement is in 50 kg bags.
Waste allowance
- 8% on the concrete, for spill, an uneven base and over-dig.
Ask your engineer to confirm
- The strength (MPa) for each part of the job is the engineer’s call, not this calculator’s.
- Above about 3 m³ in one go, ask for a ready-mix price as well.