Expert Guide
Concrete Calculators
Slab Concrete Calculator – Cement, Sand & Aggregate
Quality Inspector
Enter your slab dimensions and concrete mix to instantly calculate how many bags of cement, cubic metres of sand, and cubic metres of aggregate you need for casting the slab.
📐 Formula & Method
Wet volume = Length × Width × Thickness. Dry volume = Wet volume × 1.54. Based on mix ratio, cement = Dry Volume / (Sum of ratio parts). Sand and aggregate are proportional fractions.
Wet Volume = L × W × T
Dry Volume = Wet Volume × 1.54
For M20 (1:1.5:3), Sum of parts = 5.5
Cement (m³) = Dry Volume × (1/5.5)
Cement (bags) = Cement (m³) / 0.0347
📋 Worked Example
For a 10m × 6m × 0.15m slab with M20 concrete: • Wet Volume = 9 m³ • Dry Volume = 9 × 1.54 = 13.86 m³ • Cement = 13.86/5.5 = 2.52 m³ → ≈ 73 bags
❓ Frequently Asked Questions
When dry materials are mixed with water they compact. To get 1 cubic metre of wet concrete, you need about 1.54 cubic metres of dry mix.
M20 (1:1.5:3) is the standard and most commonly used grade for residential slabs and general RCC work.
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