Concrete volume = Length x Width x Depth (all in metres). Example: 4m x 3m slab, 10cm thick = 4 x 3 x 0.10 = 1.2m³. For site mixing, 1m³ needs approximately 7 x 50kg cement bags, 0.65m³ sand, and 0.9m³ coarse aggregate. Always add 10% extra for waste and uneven ground. Ready-mix concrete is ordered in cubic metres (m³).
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🧱 Concrete Calculator
Calculate concrete volume for slabs, driveways, foundations, and columns. Get ready-mix quantities and site-mix materials (cement bags, sand, aggregate). Free and instant.
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The 365tool.net Concrete Calculator uses standard construction volume formulas. Material quantities are estimates based on standard 1:2:3 mix ratio. Consult a structural engineer for load-bearing foundations. Free for homeowners and contractors. No sign-up needed.
🤔 How Does This Work?
Concrete volume calculation:
Slab: Volume = Length x Width x Thickness (all in metres)
Column: Volume = π x (diameter/2)² x Height x Count
Add 10% waste for uneven ground and spillage
Materials per m³: 7 bags cement, 0.65m³ sand, 0.9m³ aggregate
❓ Frequently Asked Questions
What concrete mix is best for home use?▼
Standard mix 1:2:3 (cement:sand:aggregate by volume) gives 20-25 MPa — suitable for most home applications: driveways, footpaths, garden slabs, non-structural footings. For structural elements (beams, columns, foundations): use 1:1.5:3 for stronger M25 concrete. For decorative work: add plasticiser for better workability.
Ready-mix vs site mixing?▼
Ready-mix pros: consistent quality, no mixing labour, ideal for large pours (over 1m³). Cons: minimum order quantities, scheduling required, higher cost per m³. Site mixing pros: flexible quantity, lower material cost, good for small jobs. Cons: labour intensive, quality depends on mixing, slower. For over 2m³, ready-mix is usually more economical when labour costs are included.
How long does concrete take to cure?▼
Initial set: 24-48 hours (can walk on it lightly). Strength at 7 days: about 65% of final strength. Full strength at 28 days: design strength achieved. Keep concrete moist for the first 7 days for proper curing — cover with plastic or wet burlap. Avoid heavy traffic for 7 days. Vehicle traffic should wait until 28 days for full strength.
How much concrete does a bag of cement make?▼
One 50kg cement bag makes approximately: with 1:2:3 mix — about 0.15m³ of concrete. So 1m³ requires about 6-7 bags of cement. A standard pre-bagged concrete mix (cement + aggregate combined) typically covers 0.01-0.02m³ per 20-25kg bag — much more expensive per m³ but convenient for very small jobs.
What is reinforced concrete?▼
Reinforced concrete (RC) adds steel rebar or mesh within the concrete to handle tensile (stretching) forces that plain concrete cannot withstand. Plain concrete is strong in compression but weak in tension — it cracks under pulling or bending forces. Rebar handles the tension, concrete handles the compression. Required for: beams, columns, structural slabs, retaining walls.
Standard mix 1:2:3 (cement:sand:aggregate by volume) gives 20-25 MPa — suitable for most home applications: driveways, footpaths, garden slabs, non-structural footings. For structural elements (beams, columns, foundations): use 1:1.5:3 for stronger M25 concrete. For decorative work: add plasticiser for better workability.
Ready-mix vs site mixing?▼
Ready-mix pros: consistent quality, no mixing labour, ideal for large pours (over 1m³). Cons: minimum order quantities, scheduling required, higher cost per m³. Site mixing pros: flexible quantity, lower material cost, good for small jobs. Cons: labour intensive, quality depends on mixing, slower. For over 2m³, ready-mix is usually more economical when labour costs are included.
How long does concrete take to cure?▼
Initial set: 24-48 hours (can walk on it lightly). Strength at 7 days: about 65% of final strength. Full strength at 28 days: design strength achieved. Keep concrete moist for the first 7 days for proper curing — cover with plastic or wet burlap. Avoid heavy traffic for 7 days. Vehicle traffic should wait until 28 days for full strength.
How much concrete does a bag of cement make?▼
One 50kg cement bag makes approximately: with 1:2:3 mix — about 0.15m³ of concrete. So 1m³ requires about 6-7 bags of cement. A standard pre-bagged concrete mix (cement + aggregate combined) typically covers 0.01-0.02m³ per 20-25kg bag — much more expensive per m³ but convenient for very small jobs.
What is reinforced concrete?▼
Reinforced concrete (RC) adds steel rebar or mesh within the concrete to handle tensile (stretching) forces that plain concrete cannot withstand. Plain concrete is strong in compression but weak in tension — it cracks under pulling or bending forces. Rebar handles the tension, concrete handles the compression. Required for: beams, columns, structural slabs, retaining walls.