Find how many cement bags and how much sand and aggregate (gitti) you need for any concrete grade from M5 to M25 or a custom ratio. Results in bags, kg, cubic metres, CFT and brass, plus water.
Formula checked 23 Oct 2026Free · no sign-up
Was this calculator helpful?
Found a bug or have a suggestion?
Leave it here and we will fix it and reply to you.
Embed this calculator on your website (free)
Copy this code into your page. It stays free and updates automatically.
How to use this calculator
Enter the wet volume of concrete, or switch to length × width × thickness (for example a slab 10 ft × 10 ft × 4 in).
Choose the grade — M20 for RCC slabs, beams and columns, M15 for floors, M7.5–M10 for PCC beds.
Keep the dry volume factor at 1.54 unless your engineer specifies otherwise.
Choose the cement bag size and water–cement ratio. Add wastage (2–5%) if you want a buffer.
The dry volume method (formula)
Dry volume = Wet volume × 1.54
Cement (m³) = Dry volume × cement part ÷ total parts
Cement bags = Cement (m³) × 1,440 ÷ 50
Sand (m³) = Dry volume × sand part ÷ total parts
Aggregate = Dry volume × aggregate part ÷ total parts
1 m³ = 35.3147 CFT · 1 brass = 100 CFT
Worked example: 1 m³ of M20 (1 : 1.5 : 3)
Dry volume = 1 × 1.54 = 1.54 m³; total parts = 1 + 1.5 + 3 = 5.5
All values use the 1.54 dry volume factor and cement at 1,440 kg/m³, with no wastage. Many site engineers add 2–5% for wastage on top.
Practical tips
Sand bulking: damp sand swells by 20–30% in volume. If you measure sand in boxes or wheelbarrows, buy a little more.
Use the right aggregate size: 20 mm aggregate is standard for RCC; 40 mm for PCC and mass concrete.
Mix by weight on big jobs. Volume batching with boxes (farma) is common on small sites, but weight batching is more accurate.
Cure for at least 7 days (10–14 days with blended cements). Curing matters as much as the mix.
For M25 and above, use a design mix from a testing laboratory as recommended by IS 456 and IS 10262.
Frequently asked questions
How many cement bags are needed for 1 cubic metre of M20 concrete?
About 8.06 bags of 50 kg. M20 is mixed 1 : 1.5 : 3. Dry volume = 1 × 1.54 = 1.54 m³, cement = 1.54 × 1 ÷ 5.5 = 0.28 m³, and 0.28 × 1,440 kg/m³ = 403.2 kg ÷ 50 = 8.06 bags.
Why multiply by 1.54 for dry volume?
Dry cement, sand and aggregate contain air gaps. When water is added and the mix is compacted, the volume reduces. Engineers allow about 52–57% extra dry material, so 1 m³ of wet concrete needs about 1.54 m³ of dry ingredients.
What is the density of cement and the volume of one bag?
Cement is taken as 1,440 kg/m³ in these calculations. One 50 kg bag is therefore 50 ÷ 1,440 = 0.0347 m³, or about 1.23 CFT.
What is 1 brass of sand?
Brass is a unit used in India for sand and aggregate. 1 brass = 100 cubic feet = 2.83 cubic metres. The calculator shows brass for sand and aggregate.
Are nominal mix ratios still allowed for M25 and above?
IS 456 allows nominal mixes up to M20. For M25 and higher grades, a design mix tested in a laboratory is recommended. The 1 : 1 : 2 ratio for M25 is only an approximate guide.
How much water is needed?
Water = cement weight × water–cement ratio. For 403 kg of cement at 0.5, you need about 202 litres, less if the sand is wet. Adding extra water weakens concrete.
How we checked this calculator
We test this tool against worked examples before every release (last check: 23 Oct 2026, version 1.0.0). Results are estimates for planning — confirm critical figures with your supplier or a qualified professional.
