Concrete Calculators

The most common nominal mix is 1:2:4 (cement : sand : coarse aggregate) by volume, which roughly corresponds to M15 grade concrete with a compressive strength of about 15 MPa after 28 days. For structural elements like beams and columns, 1:1.5:3 (M20) is typically the minimum specified by building codes. Always confirm the required grade with your structural engineer before ordering materials.

A 10 × 10 ft slab at 5 inches thick has a wet volume of about 1.18 cubic meters. After accounting for the 52 % dry-volume increase and using a 1:2:4 mix, you need roughly 7 bags of 50 kg cement (or 8.4 bags of the smaller 40 kg variety). Use the concrete calculator on this page to get the exact number for your specific slab dimensions and chosen mix ratio.

Ready-mix concrete (RMC) is batched at a central plant with precise water-cement ratios, delivered by transit mixer, and best suited for large pours where consistency matters — think raft foundations or multi-story slabs. Site-mixed concrete is prepared on location using a mechanical mixer or by hand, which works well for smaller jobs like boundary walls or patch repairs. RMC costs more per cubic meter but saves labor time and generally yields higher, more uniform strength.

Use the formula V = π × r² × h, where r is the radius and h is the height (or depth) of the column or footing. For example, a circular column 300 mm in diameter and 3 m tall has a volume of π × 0.15² × 3 ≈ 0.212 m³. Multiply this by the number of columns, then apply the dry volume factor (× 1.52) and your mix proportions to get cement, sand, and aggregate quantities.