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Concrete Calculator
Calculate concrete volume, cement bags, sand and aggregate quantities for slabs, columns, beams and footings. Supports M10 to M30 mix ratios. Enter your dimensions and get instant material quantities and cost estimate — no signup required.
Uses standard dry volume factor of 1.54. Material prices editable for local rates.
Concrete Calculator
Volume · Cement Bags · Sand · Aggregate · Total Cost
RCC slabs, beams, columns (standard)
▬ Slab▌ Column━ Beam⬛ Footing▪ Wall
Default prices are approximate BD 2024 market rates. Update them to match your local supplier prices for accurate cost.
How to Use
- 1Select the concrete mix grade (M20 is standard for most residential work).
- 2Choose your dimension unit — feet, metres or inches.
- 3Enter Length, Width, and Depth/Thickness of the element.
- 4Set your wastage percentage (5% minimum, 10% recommended).
- 5Enter local prices for cement (per bag), sand and aggregate (per m³).
- 6View volume, material quantities and total material cost instantly.
Example: Roof Slab
- Mix grade: M20 (1:1.5:3)
- Slab: 20 ft × 15 ft × 0.5 ft thick
- Wastage: 5%
- Wet volume: 1.50 m³
Result: ~15 bags cement · 0.56 m³ sand · 1.12 m³ aggregate
Formula Used
Wet Volume = L × W × D. Dry Volume = Wet Volume × 1.54 × (1 + wastage%). Cement = (1 / total parts) × Dry Volume × 1,440 kg/m³ ÷ 50 kg/bag. Sand and aggregate volumes are calculated proportionally from the mix ratio. This is the standard method used by civil engineers globally.
Concrete Mix Tips
- 1Always add 5–10% wastage to account for spillage, over-filling of forms, and cracks
- 2Use river sand (coarse to medium) — avoid fine sea sand for structural concrete
- 320mm aggregate is standard for slabs and columns in Bangladesh
- 4Water-cement ratio should not exceed 0.5 for M20 and above — too much water weakens concrete
- 5Curing concrete for at least 14 days significantly increases its final strength
- 6Use a vibrator during pouring to eliminate air pockets in the mix
- 7Never mix concrete in extreme heat (above 35°C) without shade or chilled water
- 8Store cement bags off the ground on wooden planks and cover with plastic to prevent moisture
Frequently Asked Questions
How does the concrete calculator work?
It calculates wet concrete volume from your dimensions (Length × Width × Depth). It then multiplies by a dry volume factor of 1.54 (to account for voids and compaction) and splits the result into cement, sand and aggregate quantities based on your selected mix ratio. A wastage percentage is added on top.
What is the dry volume factor and why 1.54?
When dry materials (cement, sand, aggregate) are mixed with water and compacted, they reduce in volume. To produce 1 m³ of wet concrete, you need approximately 1.54 m³ of dry materials. This 1.54 factor is the standard used by civil engineers worldwide.
Which concrete mix grade should I use?
M10 (1:3:6) is used for lean concrete and bedding. M15 (1:2:4) is used for foundations, footpaths and mass concrete. M20 (1:1.5:3) is the most common for residential RCC slabs, beams and columns. M25 (1:1:2) is for high-strength structures. M30 and above are for bridges and heavy-duty industrial structures.
How many cement bags are needed for a 1,000 sqft roof slab?
For a standard 1,000 sqft roof slab (4.5 inch or ~115 mm thick) using M20 mix: approximately 85–100 bags of 50 kg cement. Use this calculator for precise values by entering your exact dimensions.
What is the standard slab thickness in Bangladesh?
For residential buildings in Bangladesh, RCC roof slabs are typically 4.5 to 5 inches (115–125 mm) thick. Ground floor slabs on grade may be 4 inches. For longer spans or heavier loads, 5.5 to 6 inches (140–150 mm) is used. Always follow your structural engineer's design.
Does the calculator include labour cost for concrete?
No. The cost estimate covers materials only (cement bags, sand, and aggregate). Labour, scaffolding, formwork, curing, and mixing equipment costs are not included. Add 20–30% on top of material cost for a complete concrete works estimate.
Can I use this calculator for columns and beams?
Yes. Simply enter the cross-section dimensions (Length × Width × Depth) of your column or beam. For multiple identical elements, multiply your result by the number of elements.
What is the unit weight of cement, sand and aggregate?
This calculator uses: Cement density = 1,440 kg/m³ (1 bag = 50 kg), Dry sand density = 1,600 kg/m³, Coarse aggregate (gravel) density = 1,500 kg/m³. These are standard values used in civil engineering calculations.