Cement and Sand Calculator
Calculate cement bags, sand and gravel for concrete, screed and mortar by ratio (1:3, 1:4, 1:6, etc.). Everything in your browser.
Concrete and mortar mix calculation
Mix ratios are given by volume. Use 1:3:3 (cement:sand:gravel) for non-structural concrete, and 1:2:3 or 1:1.5:2.5 for structural work with a defined fck. One cubic metre of residential fck 25 MPa concrete takes roughly 350 kg cement, 850 kg sand, 1050 kg gravel and 175 L water, a w/c ratio near 0.5. Since a cement bag holds 50 kg, that comes to about 7 bags per m³. For sand, go with washed medium grade for mortar and coarse for concrete; gravel runs grades 0, 1 and 2 by increasing diameter. Render mortar uses 1:3 (cement:sand). As an example, a 2 m³ slab at 1:2:3 needs about 14 bags of cement, 1.7 m³ sand and 2.6 m³ gravel.
Applications and standards
It helps estimate materials for slabs, foundations, subfloors, retaining walls and the budgeting of a renovation. The relevant Brazilian standards are NBR 12655 (concrete production and acceptance), NBR 6118 (reinforced concrete structures) and NBR 7211 (aggregates). On structural work, always follow the structural engineer's spec. The calculator gives you a rough number, not a design.
FAQ
Why does the same mix give different m³? The materials pack together once mixed, so 1 m³ of dry sand plus cement plus gravel yields less than 1 m³ of wet concrete. The calculator already factors in the typical packing.
What about water? Strength comes down to the water/cement ratio (a/c): use 0.5 for fck 25 and 0.45 for higher strength. Too much water and the concrete ends up weaker.
Is ready-mix concrete cheaper? Past 5 m³, usinated concrete usually wins on both price and consistency compared with mixing on site. Below that, people tend to mix on-site with a small mixer.
Related Tools
Mortar Mix Calculator
Calculate the cement and sand needed for a mortar or render mix from the volume and the ratio. Buy the right amount of material for the job.
Aggregate Fineness Modulus
Calculates the fineness modulus of an aggregate by adding the cumulative percentages retained on the eight standard sieves and dividing by one hundred. Note that the input is the CUMULATIVE retained percentage, not the passing nor the individual retained — that is where the calculation usually goes wrong. Concrete sand normally lands between 2.2 and 3.1. Enter the eight percentages.
Concrete Mix Calculator
Estimate cement, sand, gravel and water for a given concrete amount based on the mix ratio (e.g., 1:2:3) and target volume.
Wall Concrete Volume
Compute concrete volume m³ + cement/sand/gravel estimates for a wall.
Concrete Shrinkage Loss
Calculate the prestress loss from concrete shrinkage, Δσ = ε_cs·E_s, from the shrinkage strain ε_cs (dimensionless) and the steel modulus E_s (MPa). Shrinkage is the volume reduction concrete undergoes over time as it LOSES water by evaporation (drying shrinkage) and through cement hydration reactions (autogenous shrinkage), independent of loading. When the concrete of a prestressed member shrinks (shortens), the bonded steel tendon shortens too — and shortening, it LOSES tension, exactly as in elastic-shortening loss, except here the shortening is from shrinkage and occurs SLOWLY over months and years. The loss is simply the shrinkage strain times the steel modulus (the stress that shortening 'steals' from the tendon). The shrinkage strain ε_cs is typically 0.0002-0.0005 (200-500 microstrains) and depends on ambient humidity (drier = more shrinkage), member dimensions (thin members shrink more, losing water faster), mix and time. It is one of the three time-dependent losses (with creep and relaxation) reducing prestress over the structure's life. Enter the shrinkage strain and the steel modulus.
Gable Flashing by Height
Estimates meters of gable flashing from length and gable height.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.