Concrete Mix Calculator (Cement, Sand, Aggregate)
Calculate the exact number of cement bags, and cubic feet (CFT) of sand and aggregate required for various concrete grades.
Concrete Mix Calculator: Find Cement, Sand, and Aggregate Quantities
Whether you are casting a roof slab (lanter), building columns, or laying a foundation, getting the right mix of materials is vital for the structural integrity of your building. Our cement sand aggregate calculator uses the standard Indian nominal mix methods to determine exactly how many 50kg cement bags and CFT of sand and aggregate you need.
Understanding Concrete Mix Ratios in India
Concrete is classified into different grades (M10, M15, M20, M25). The "M" stands for Mix, and the number represents the compressive strength of the concrete after 28 days (in N/mm²). Each grade corresponds to a specific volume ratio of Cement : Sand : Aggregate.
- M10 (1:3:6): Low strength. Used for leveling courses (PCC) beneath foundations.
- M15 (1:2:4): Medium strength. Often used for simple residential foundations or non-load-bearing ground floors.
- M20 (1:1.5:3): The standard structural mix. The M20 concrete mix ratio is universally recommended for RCC roof slabs, beams, and columns in standard Indian house construction.
- M25 (1:1:2): High strength. Used for heavy load-bearing structures and commercial buildings.
The Dry Volume Factor (The 1.54 Rule)
When you mix water with dry cement, sand, and aggregate, the mixture shrinks because the finer cement and sand particles fill the empty voids between the large aggregate stones.
To get 1 cubic meter of wet, poured concrete, you actually need 54% more dry material. Therefore, in all civil engineering calculations, we multiply the required wet volume by 1.54 to get the dry volume.
Step-by-Step Example: Calculating 1 Cubic Meter of M20 Concrete
Let's look at the exact mathematical formula to find the materials needed for 1 m³ of M20 grade concrete.
Step 1: Find the Dry Volume
Wet Volume = 1 m³.
Dry Volume = 1 m³ × 1.54 = 1.54 m³.
Step 2: Apply the M20 Ratio
The M20 concrete mix ratio is 1 : 1.5 : 3.
Total parts = 1 + 1.5 + 3 = 5.5 parts.
Formula: (Cement Part / Total Parts) × Dry Volume
Volume of Cement = (1 / 5.5) × 1.54 = 0.28 m³.
Weight of Cement = 0.28 m³ × 1440 kg/m³ (Density) = 403.2 kg.
Number of Bags = 403.2 kg ÷ 50 kg = ~8 Bags of Cement.
Formula: (Sand Part / Total Parts) × Dry Volume
Volume of Sand = (1.5 / 5.5) × 1.54 = 0.42 m³.
Convert to CFT (multiply by 35.3147) = 0.42 × 35.3147 = 14.8 CFT of Sand.
Formula: (Aggregate Part / Total Parts) × Dry Volume
Volume of Aggregate = (3 / 5.5) × 1.54 = 0.84 m³.
Convert to CFT = 0.84 × 35.3147 = 29.7 CFT of Aggregate.
Note: For massive projects, you can convert the total CFT of sand and aggregate into Brass simply by dividing the CFT result by 100!