Concrete Calculator
Calculate concrete volume, cement bags, sand, and gravel for slabs and columns
Shape
Length (m)
m
Width (m)
m
Thickness (cm)
cm
Ready-mix Price (₹/m³, optional)
₹
Mix Ratio Used: 1:2:4
Per 1 m³ of concrete:
• Cement: ~320 kg (~6.4 bags of 50 kg)
• Sand: ~0.44 m³
• Gravel/aggregate: ~0.88 m³
Add 10–15% waste for cuts & spillage
Concrete Volume
—
Estimated cost: —
Cement Bags (50 kg)—
Sand Required—
Gravel/Aggregate—
Concrete Mix Ratios Explained
The 1:2:4 mix ratio (cement : sand : coarse aggregate by volume) is the standard M15 grade concrete used for general construction. Higher grades like M20 (1:1.5:3) use more cement for greater strength — for RCC columns and slabs in load-bearing structures.
This calculator outputs dry material quantities. In practice, mix 10–15% extra to account for voids, compaction, and spillage. Ready-mix concrete (RMC) is priced per m³ and delivered pre-mixed — convenient for large pours.
lightbulb Example
Slab: 5m × 4m × 15 cm thick:
1Volume = 5 × 4 × 0.15 = 3 m³
2Cement = 3 × 320 = 960 kg = 20 bags
3Sand = 3 × 0.44 = 1.32 m³
✓ Gravel = 3 × 0.88 = 2.64 m³
quizFrequently Asked Questions
How much does 1 bag of cement cover?
A standard 50 kg bag of cement, mixed in a 1:2:4 ratio, yields approximately 0.035 cubic metres (35 litres) of concrete. For M20 grade mix (1:1.5:3), you need roughly 8 bags per cubic metre. Always add 5–10% for wastage. Exact consumption depends on the mix design and whether batching is done by volume or weight.
What concrete grade should I use for house construction?
M20 (20 N/mm² strength) is the minimum for reinforced concrete slabs, beams, and columns in residential construction. Foundations use M15 for plain concrete (PCC) or M20 for RCC footings. High-rise buildings and exposed structures use M25–M35. Always follow the structural engineer's specifications — never substitute a lower grade to save cost.
How do I prevent concrete from cracking?
Use the correct water-cement ratio (typically 0.4–0.5 for M20) and avoid adding excess water. Cure the concrete by keeping it moist for a minimum of 7 days (28 days for full strength). Avoid placing concrete in extreme heat. Add control joints every 3–4 metres for slabs to guide any cracking to predetermined lines.