Concrete Mix Ratio Calculator
Turn a concrete mix ratio (1:2:3, 1:2:4, 1:1.5:3…) and a volume into bags of cement, sand, gravel and water — with the 1.54 dry-volume factor, waste and every nominal mix compared.
How it works
dry volume = wet volume × (1 + waste) × 1.54 · cement = dry volume × c ÷ (c + s + g) × 1,440 kg/m³ · sand = dry volume × s ÷ (c + s + g) · gravel = dry volume × g ÷ (c + s + g) · water = cement kg × w/c ratio
A nominal mix gives the proportions of cement, sand and coarse aggregate by volume. Because loose dry materials shrink when water fills the voids, the dry volume needed is about 54% more than the finished concrete (the 1.54 factor used in IS 456 practice). Each share of that dry volume is converted to mass with typical bulk densities — cement 1,440 kg/m³, sand 1,600 kg/m³, gravel 1,500 kg/m³ — and the water follows from the water–cement ratio, the single biggest driver of strength. For structural work above about 20 MPa, a designed mix by weight (ACI 211 or a ready-mix supplier) replaces nominal ratios.
Worked example
For 1 m³ of 1:2:3 concrete with 5% waste: dry volume = 1 × 1.05 × 1.54 = 1.617 m³. Cement = 1.617 × 1/6 × 1,440 = 388 kg, which is 7.8 → 8 bags of 50 kg; sand = 1.617 × 2/6 = 0.54 m³ (862 kg); gravel = 1.617 × 3/6 = 0.81 m³ (1,213 kg); water at w/c 0.5 = 194 L.
Sources: IS 456:2000 Plain and Reinforced Concrete — nominal mixes (Bureau of Indian Standards) · PCA — Design and Control of Concrete Mixtures
Frequently asked questions
What does a 1:2:3 concrete mix mean?
One part cement, two parts sand and three parts gravel by volume. It is the classic general-purpose mix for slabs, footings and driveways, giving roughly 17–21 MPa (2,500–3,000 psi) when the water–cement ratio is kept near 0.5.
Why multiply by 1.54?
Dry sand and gravel contain air voids that the cement paste fills, so the loose materials needed are about 52–57% more than the finished volume. 1.54 is the factor commonly used for site estimates; some guides use 1.52 or 1.57.
How many bags of cement are in a cubic metre of concrete?
About 6 bags of 50 kg for 1:2:4, 7–8 for 1:2:3, 8 for 1:1.5:3 and 11 for 1:1:2 — before waste. Richer mixes need more cement and are stronger, provided you do not add extra water.
How much water should I add?
Water = cement weight × the water–cement ratio. At 0.5, a 50 kg bag takes 25 L. Damp sand already carries 2–5% water, so add less on site and stop when the mix is workable; every extra litre lowers strength.
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This calculator is for educational purposes. Double-check important results before acting on them.