Concrete, Cement & Sand Calculator (Roof Slab RCC)

Formula & Calculation Methodology

Dry Volume = Wet Volume (L × W × Thickness) × 1.54 bulking factor; Material quantities determined by IS 456 mix proportions (M20 = 1:1.5:3).

Step-by-Step Worked Example

House Slab: 40 ft × 30 ft (1,200 sq ft) | Thickness: 5 inches | Mix Grade: M20 (1:1.5:3)

1. Wet Volume = 40 × 30 × (5 ÷ 12) = 500 Cubic Feet (14.16 m³)
2. Dry Volume (+54% void factor) = 14.16 × 1.54 = 21.80 m³
3. Cement (1 part of 5.5) = (1 ÷ 5.5) × 21.80 × 28.8 bags/m³ = 115 Bags (50kg)
4. Sand Reti (1.5 parts) = 209 Cu Ft (~2.09 Brass / 94 Quintals)
5. Coarse Aggregate Gitti (3 parts) = 418 Cu Ft (~4.18 Brass / 200 Quintals)
6. Water Required = 115 × 28 Litres = 3,220 Litres

Standard Concrete Mix Grades for House Construction in India

M20 Grade (1 Cement : 1.5 Sand : 3 Aggregate) is the Bureau of Indian Standards (BIS IS 456:2000) recommended mix for residential RCC roof slabs, beams, and stairs.

M15 Grade (1:2:4) is used for plain cement concrete (PCC) flooring, while M25 Grade (1:1:2) is used for heavy load-bearing pillars and foundations.

Frequently Asked Questions