Concrete Mix Calculator – Cement, Sand & Aggregate

It is an illustrative volumetric proportion: one part cement, two parts fine aggregate (sand), and four parts coarse aggregate. These are relative parts, not “one cement bag and two sand bags” by default. Since bag masses and loose-material densities differ, this calculator estimates cement mass or whole 50 kg cement bags and sand/aggregate volumes separately. A nominal ratio cannot guarantee a strength grade.

Worked example: For a 5 m × 4 m × 0.1 m slab, wet volume is 2.00 m³. With 5% allowance it becomes 2.10 m³. At an illustrative dry-volume factor of 1.54, dry constituent volume = 3.234 m³. For a nominal 1:2:4 volumetric ratio (seven parts), estimated cement = (3.234 ÷ 7) × 1,440 ≈ 665 kg, or 14 × 50 kg cement bags rounded up; sand = 3.234 × 2/7 = 0.924 m³; aggregate = 3.234 × 4/7 = 1.848 m³. Actual batching, water, moisture and mix strength require an approved design.

First choose an appropriate, approved estimating basis. For an illustrative 1:2:4 ratio and dry factor 1.54, cement takes 1/7 of 1.54 m³ = 0.220 m³ bulk volume. At the calculator’s assumed bulk density of 1,440 kg/m³, cement is about 317 kg, or ceil(317/50) = 7 whole 50 kg cement bags. This is a quantity estimate, not a concrete mix design.

Concrete contains aggregate voids and experiences differences between loose dry ingredient volume and compacted placed yield. A dry-volume factor is a conventional simplifying multiplier in some volumetric planning methods. The calculator defaults to 1.54 but makes it editable because there is no single factor valid for every material, moisture condition or batching method. Project testing and approved proportions take priority.

Do not assume a simple nominal ratio certifies M25, M30 or any other structural grade. Strength and durability depend on water-to-cement ratio, materials, grading, admixtures, compaction, curing and a proper design and testing process. For specified or structural grades, obtain an approved mix design from a qualified professional or supplier. This page estimates ingredient quantities from approved inputs; it does not design concrete.

After volume and allowance, multiply the wet concrete volume by the selected dry-volume factor. Divide that estimated dry volume among cement, fine aggregate and coarse aggregate according to the ratio parts. For a 1:2:4 ratio, sand is 2/7 of dry volume and coarse aggregate is 4/7. The outputs are loose ingredient planning volumes and need site adjustment for moisture, bulking, grading and supplier measure conventions.

This depends on the actual approved water-to-cement ratio and the moisture already present in the aggregates. When a ratio is supplied, the tool multiplies estimated cement mass by that ratio to give an approximate water mass, shown in litres. Do not blindly add this amount to a wet aggregate mix; too much water can change workability, reduce strength and affect durability.

Enter the finished concrete geometry first. The engine calculates the placed wet concrete volume, adds any project allowance, and then derives a separate dry ingredient quantity using the selected factor. Do not multiply the physical volume by the dry factor before entering it; that would apply the same expansion twice.

No. An approved mix design involves strength class, durability and exposure class, concrete workability, material testing, cement content, aggregate grading, admixtures and quality control. The calculator is for estimates from stated inputs; it does not certify structural concrete or substitute for site inspection, trial batches, laboratory tests or contractual project requirements.