Construction Material Calculator
Estimate cement bags, sand, aggregate and bricks for concrete, brick walls and plaster.
| Step | Working | Result |
|---|---|---|
| Wet volume | 12 × 10 ft × 5 inch | 1.416 m³ |
| Dry volume | × 1.54 | 2.18 m³ |
| Mix | 1 : 1.5 : 3 (total 5.5 parts) | M20 |
| Cement | 2.18 × 1/5.5 | 0.396 m³ |
| Cement bags | 0.396 ÷ 0.0347 m³ per bag | 11.42 |
| Sand | 2.18 × 1.5/5.5 | 0.595 m³ |
| Aggregate | 2.18 × 3/5.5 | 1.189 m³ |
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Results are for general guidance. Please check anything important before relying on it. Terms of use
How to Use
- Choose what to estimate: Concrete, a Brick wall or Plaster. Then choose feet and inches or metres and mm.
- For concrete, enter the length, width and thickness, and pick the grade (M20, M15, M10…).
- For a brick wall, enter the wall's length and height and any door or window area to subtract, then pick the brick size, wall thickness and mortar mix.
- For plaster, enter the wall area and pick the thickness and mix.
- Read the cement bags, sand (m³, cft, brass and tonnes), aggregate and bricks. The method table shows every step so you can check it with your engineer or contractor.
Estimating cement, sand, aggregate and bricks
Before you buy materials for a slab, a wall or plastering, it helps to know roughly how many cement bags and how much sand and aggregate to order. This calculator uses the rules of thumb taught in Indian civil engineering courses and used on most small sites. Actual use depends on the materials, how they are measured and the workmanship, so treat the results as a starting estimate and confirm big orders with your engineer.
Concrete: the dry volume method
Cement (m³) = dry volume × cement parts ÷ total parts
Cement bags = cement m³ ÷ 0.0347 (50 kg ÷ 1,440 kg/m³)
Sand, aggregate = dry volume × their parts ÷ total parts
Wet concrete takes up less space than the loose dry materials that go into it, because the cement and sand fill the gaps between the stones. Sites allow for this with a factor of about 1.52–1.57, most often 1.54.
| Grade | Nominal mix (C : S : A) | Cement per m³ | Sand per m³ | Aggregate per m³ |
|---|---|---|---|---|
| M20 | 1 : 1.5 : 3 | 8.06 bags | 0.42 m³ | 0.84 m³ |
| M15 | 1 : 2 : 4 | 6.34 bags | 0.44 m³ | 0.88 m³ |
| M10 | 1 : 3 : 6 | 4.44 bags | 0.46 m³ | 0.92 m³ |
Worked example: a 12 × 10 ft roof slab, 5 inches thick, is 1.416 m³ (50 cft). For M20: dry volume 1.416 × 1.54 = 2.18 m³. Cement = 2.18 ÷ 5.5 = 0.396 m³, which is 11.4 bags, so buy 12. Sand = 0.595 m³ (21 cft) and 20 mm aggregate = 1.19 m³ (42 cft).
IS 456:2000, the Indian code for plain and reinforced concrete, allows nominal mixes only for grades up to M20 and sets M20 as the minimum grade for reinforced concrete. The volume ratios above are the traditional site proportions. For M25 and above, and for any large structure, use a design mix or ready-mix concrete specified by your structural engineer.
Brickwork
× 2 for a full-brick wall
Wet mortar = wall volume − volume of the bricks
Dry mortar = wet mortar × 1.33
IS 1077 lists a modular brick of 190 × 90 × 90 mm, and many kilns still make the older 230 × 110 × 70 mm size. With 10 mm joints, a full-brick (230 mm, "9 inch") wall of traditional bricks takes about 104 bricks per m² of wall face, and a half-brick (110 mm, "4.5 inch") partition about 52. Brickwork is usually laid in 1 : 6 mortar for full-brick walls and a richer 1 : 4 for half-brick walls.
Example: a 6 × 3 m wall in 9-inch brickwork is 18 m² × 0.23 m = 4.14 m³. It needs 18 × 104.2 = 1,875 bricks, plus 5% for breakage = 1,969. That's 0.82 m³ of wet mortar (1.09 m³ dry), which in 1 : 6 needs about 4.5 bags of cement and 0.93 m³ of sand.
Plaster
+ 20% for uneven surfaces and filling joints
Dry mortar = × 1.33
Common thicknesses are 12 mm for inside walls (1 : 6), 15 mm on the rough side of a brick wall, 20 mm for outside walls (1 : 4 or 1 : 5) and 6 mm for ceilings (1 : 3). For 100 m² of 12 mm plaster in 1 : 6, you need about 7.9 bags of cement and 1.64 m³ of sand.
Units used on Indian sites
- 1 m³ = 35.31 cft. Sand and aggregate are often sold by the cubic foot.
- 1 brass = 100 cft (2.83 m³), a common unit for sand and aggregate in Maharashtra, Gujarat and nearby states.
- Some suppliers sell by the tonne. The calculator converts using a typical loose density of about 1.6 t/m³ for sand and 1.5 t/m³ for aggregate. Wet or compacted material weighs more, so ask your supplier.
Order 5–10% extra for spillage and site losses, and keep cement dry and off the floor. Bagged cement is best used within about three months.