Concrete Calculator: Cement Bags, Sand and Aggregate for M10–M25
Enter the size of your slab, column or footing and pick the grade. You get the concrete volume and how many 50 kg cement bags, how much sand and aggregate to order.
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Cement (50 kg bags)
21bags
- Concrete volume
- 2.5 m³ · 88.3 cft
- Sand
- 1.05 m³ · 37.1 cft
- Aggregate (20 mm)
- 2.1 m³ · 74.2 cft
- Water (w/c 0.5)
- 504 L
Estimate only, based on standard thumb rules. Confirm quantities with your engineer or contractor before you buy.
Cement needed: about 1,008 kg. Bags are rounded up.
Show working
- V = 5 × 4 × 0.125 = 2.5 m³
- V dry = 2.5 × 1.54 = 3.85 m³
- 1 : 1.5 : 3 → Σ = 5.5
- Cement = 3.85 × 1/5.5 × 1440 = 1,008 kg ÷ 50 = 20.16 → 21
- Sand = 3.85 × 1.5/5.5 = 1.05 m³; Aggregate = 3.85 × 3/5.5 = 2.1 m³
How to use
- Choose metres or feet and the shape you are casting.
- Enter the size, and the number of columns or footings.
- Pick the mix grade (M20 is common for house slabs) to see bags, sand and aggregate.
Good to know
Wet volume is length × width × thickness. Dry materials take more space before mixing, so the wet volume is multiplied by 1.54 (the standard Indian estimating factor for voids and bulking). Cement = dry volume × cement share of the mix × 1440 kg/m³, divided by 50 kg per bag.
Mix ratios are the usual nominal mixes: M10 = 1:3:6, M15 = 1:2:4, M20 = 1:1.5:3 (the volumetric equivalents of IS 456:2000 Table 9). M25 at 1:1:2 is only a site thumb rule: IS 456 expects a lab-designed mix for M25 and above, which usually needs less cement.
Sand and aggregate are shown in m³ and cubic feet (cft), because Indian suppliers often sell by cft or by brass (100 cft). Water is shown at a water–cement ratio of 0.5. Real quantities change with site wastage, moisture in sand and the engineer’s mix design, so treat this as a planning estimate.
Questions
How many cement bags are needed for 1 m³ of M20 concrete?
About 8 bags. 1 m³ × 1.54 = 1.54 m³ dry; cement is 1/5.5 of that = 0.28 m³ × 1440 = 403 kg, which is 8.06 bags of 50 kg.
Why multiply by 1.54?
Dry cement, sand and stone have air gaps that disappear when water is added, and some material is lost. Indian estimates use 1.52–1.57; 1.54 is the common middle value. You can change it under More options.
Which grade should I use for a house slab?
M20 is the minimum for reinforced concrete under IS 456 in most exposure conditions. Your structural engineer decides the grade, especially near the sea or for columns.
Does this include wastage?
Not by default. Add a wastage percentage (2–5% is common) under More options if your site loses material.
Can I use it in feet?
Yes. Switch to Feet: lengths are in feet and slab thickness, column size and diameter in inches. Results show both m³ and cft.