Concrete Mix Calculator India — M10 M15 M20 M25 M30 Per IS 456

M20 concrete uses a mix ratio of 1:1.5:3 (cement:sand:coarse aggregate). For every 1 part cement, use 1.5 parts sand and 3 parts aggregate by volume. This gives a compressive strength of 20 N/mm² after 28 days of curing.

For M20 concrete (1:1.5:3 mix), you need approximately 8 bags (50 kg each) of cement per cubic metre. The exact quantity is 403 kg/m³ of cement, which equals about 8.06 bags.

M15 has a compressive strength of 15 N/mm² and uses a 1:2:4 mix ratio. M20 has a compressive strength of 20 N/mm² and uses a 1:1.5:3 mix ratio. M20 uses more cement and is stronger, suitable for structural members like slabs and beams.

First determine total dry volume = wet volume × 1.54. For M20 (1:1.5:3), total parts = 5.5. Aggregate fraction = 3/5.5. Aggregate volume = (3/5.5) × dry volume. Multiply by unit weight (1600 kg/m³) for weight in kg.

For M25 concrete, the recommended water-cement ratio is 0.44 or less. Lower w/c ratios improve strength and durability. For ready-mix concrete and structural work, use 0.40–0.45 with a water-reducing admixture if needed.

For a 4-inch (100 mm) thick M20 slab over 100 sq ft (9.29 m²): volume = 9.29 × 0.1 = 0.929 m³. You need approximately 0.929 × 8 = 7.4 bags of cement (50 kg each). Add 5-10% for wastage.

Dry ingredients occupy more volume than when mixed with water because the voids between particles get filled. Dry volume is typically 1.54 to 1.57 times the wet (placed) volume. Always multiply the required wet volume by 1.54 to get the dry ingredient volume.

M10 concrete (1:3:6 mix, 10 N/mm² strength) is used for lean concrete below foundations, PCC (Plain Cement Concrete) in pathways, flooring underlays, and non-structural fill applications. It is not used for structural beams, columns, or slabs.

For M25 concrete (1:1:2 mix), total parts = 4. Sand fraction = 1/4. Dry volume per m³ = 1.54 m³. Sand volume = (1/4) × 1.54 = 0.385 m³. Weight = 0.385 × 1500 = 577 kg of sand per cubic metre of finished concrete.

Cement: 1440 kg/m³ (bulk density of loose cement). Fine sand: 1500–1650 kg/m³. Coarse aggregate (20mm): 1500–1600 kg/m³. These values are used to convert volumes to weights when calculating material quantities.

Calculate the volume of the footing: for a square footing of 1m × 1m × 0.5m, volume = 0.5 m³. Apply the M20 mix to find cement = 0.5 × 8 = 4 bags, sand = 0.5 × 0.44 m³ = 0.22 m³, aggregate = 0.5 × 0.88 m³ = 0.44 m³.

Nominal mix (M10-M25) uses fixed volume ratios from IS 456 without testing. Design mix is calculated by testing aggregate properties and optimizing for target strength. For structural concrete above M25, a design mix is mandatory per IS codes.

Yes. M20 (minimum grade) is specified in IS 456 for all reinforced concrete slabs, beams, and columns in moderate exposure conditions. For aggressive or coastal environments, M25 or higher is recommended for better durability.

The "M" stands for Mix, and the number represents the characteristic compressive strength of a 150mm cube specimen at 28 days curing, measured in N/mm² (or MPa). So M20 means a 20 N/mm² compressive strength at 28 days.

Admixtures like plasticizers or superplasticizers allow you to reduce the water-cement ratio while maintaining workability, resulting in higher strength. Chemical admixtures like fly ash or GGBS replace a portion of cement and improve durability. The calculator shows basic nominal mix quantities without admixtures.

For M20 concrete, 20 mm maximum size aggregate (MSA) is standard for general construction. For thin slabs or congested reinforcement, 12.5 mm or 10 mm aggregate may be used. Aggregate size affects workability and the amount of fine aggregate required.

1 cubic metre = 35.315 cubic feet. So divide cubic feet by 35.315 to get m³. For example, 100 cubic feet of concrete = 100/35.315 = 2.83 m³. The calculator accepts both units and converts automatically.

One 50 kg bag of cement yields approximately 0.035 m³ (1.25 cubic feet) of nominal M20 concrete. This includes all materials mixed together. So for 1 m³ of M20 concrete, you need about 28–29 bags (rough estimate without accounting for the proper dry volume factor).

Beam concrete volume = length × width × depth. For example, a 5m long × 0.23m wide × 0.45m deep beam = 5 × 0.23 × 0.45 = 0.5175 m³. Apply the concrete mix calculator with M20 to find the number of cement bags, sand, and aggregate required.

For M20 concrete, formwork on sides of beams can be removed after 2 days. Slab bottom formwork (props) should remain for 14–21 days. Full 28-day curing is required before applying full design loads. Wet curing (pond curing, burlap, or curing compound) must be maintained continuously.