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Concrete Mix Ratio Calculator

Calculate the quantities of cement, sand, coarse aggregate and water needed for a target concrete volume, based on a specified mix ratio and water-cement ratio.

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These calculators provide estimates and educational results. Always verify critical engineering calculations against applicable standards and qualified professional review.

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What Is It

A concrete mix ratio (like 1:2:4, cement:sand:aggregate by volume) determines the proportions of raw materials combined to reach a target strength class. Richer mixes (more cement relative to aggregate) produce higher strength but cost more; leaner mixes are economical for non-structural or mass concrete work.

How to Calculate

Enter the target volume of finished (wet, in-place) concrete you need, select a mix ratio, and set the water-cement ratio (0.5 is typical for general construction). The calculator accounts for the extra dry material volume needed before water and mixing compact the mix into its final volume, and returns cement bags, sand volume, aggregate volume and water quantity.

Example

1 m3 of concrete at a 1:2:4 mix ratio: dry volume = 1 × 1.54 = 1.54 m3, split into 1/7 cement, 2/7 sand, 4/7 aggregate by the mix parts. That works out to roughly 6.3 bags of 50kg cement, 0.44 m3 of sand, and 0.88 m3 of aggregate.

Recommendations

The 1.54 dry-volume factor is a standard rule of thumb accounting for voids between dry aggregate particles that disappear once water and cement paste fill the gaps - always use it when converting a wet, in-place volume requirement into dry material quantities.

Frequently Asked Questions

Why is dry volume larger than wet volume?

Dry aggregate and sand have air gaps between particles that get filled by cement paste and water during mixing, so you need roughly 54% more dry material volume than the final compacted wet concrete volume.

Which mix ratio should I use?

1:1.5:3 is common for structural elements needing higher strength (columns, beams, reinforced slabs); 1:2:4 is a general-purpose ratio for most residential slabs and footings; 1:3:6 is used for mass concrete, blinding layers, or non-structural fill where strength requirements are minimal.

How does this differ from the Concrete Volume Calculator?

The Concrete Volume Calculator finds how much total concrete you need from slab dimensions; this calculator takes that volume and breaks it down into the raw material quantities to actually mix or order it.

Last reviewed: 2026-09-12