Material Calculator
Concrete Calculator — Cement, Sand & Aggregate
Calculate exact cement bags, sand, aggregate, and water for M10, M15, M20, M25, M30 concrete grades. Covers slab, beam, column, footing, and staircase with full formula and worked examples.
Concrete Mix Calculator
Cement · Sand · Aggregate · Water · Cost Estimate
Quick Grade Selection:
Slab or footing length
Slab or footing width
Slab: 4–6 in · Beam depth in inches
Recommended: 5–8%
e.g. 4 columns, 2 beams
Calculation Results
Calculated—
m³
Wet Volume
—
m³
Dry Volume
—
bags
Cement (50 kg)
—
cft
Sand
—
cft
Aggregate (Crush)
—
litres
Water (approx)
—
How to Calculate Concrete — Step-by-Step Formula
Concrete calculation uses a dry-to-wet volume conversion, then splits materials by mix ratio. This is the exact method used by engineers in Pakistan, India, Saudi Arabia, and UAE.
1
Calculate Wet Volume
Wet Volume = Length × Width × Depth (in metres). This is the actual volume of concrete you pour into the formwork. Convert feet to metres by multiplying by 0.3048, and inches to metres by dividing by 39.37.
2
Apply Dry Volume Factor (× 1.54)
Dry Volume = Wet Volume × 1.54. This critical factor accounts for voids between particles and shrinkage during mixing. Skipping this step causes a 35–40% material shortage on site.
3
Calculate Cement Quantity
Cement (m³) = [Cement Part ÷ Total Parts] × Dry Volume. Then: Cement (kg) = m³ × 1440 kg/m³. Cement (bags) = kg ÷ 50. For M20 (1:1.5:3) — Total parts = 5.5, so Cement = (1/5.5) × Dry Volume.
4
Calculate Sand & Aggregate
Sand (m³) = [Sand Parts ÷ Total Parts] × Dry Volume. Aggregate (m³) = [Agg Parts ÷ Total Parts] × Dry Volume. Convert m³ to cubic feet by multiplying by 35.3147.
5
Calculate Water Required
Water (L) = Cement weight (kg) × Water-Cement Ratio (0.45 for M20). Never exceed W/C = 0.50 — excess water is the leading cause of weak concrete in Pakistan.
Wet Volume (m³) = Length(m) × Width(m) × Depth(m) × Qty × (1 + Waste%)
Dry Volume (m³) = Wet Volume × 1.54 ← bulkage + shrinkage factor
For M20 Grade (1:1.5:3) — Total parts = 1+1.5+3 = 5.5:
Cement (m³) = (1/5.5) × Dry Volume
Cement (kg) = Cement(m³) × 1440
Cement (bags) = Cement(kg) ÷ 50
Sand (cft) = (1.5/5.5) × Dry Volume × 35.3147
Aggregate(cft) = (3/5.5) × Dry Volume × 35.3147
Water (L) = Cement(kg) × 0.45
The 1.54 dry volume factor is used universally across IS 456, ACI 318, BS 8110, and all standard engineering codes. It accounts for approximately 33% void space in aggregate and 20% void space in sand.
Concrete Grade Reference — Strength, Mix Ratio & Use Cases
Choosing the right concrete grade is critical for structural safety and economy. Using a weaker grade than specified is a building code violation in Pakistan.
| Grade | Mix Ratio (C:S:A) | Strength (fck) | Cement per m³ | Standard Use in Pakistan |
|---|---|---|---|---|
| M7.5 | 1:4:8 | 7.5 MPa | ~155 kg | Mass concrete, bulk filling only |
| M10 | 1:3:6 | 10 MPa | ~210 kg | PCC levelling course, pathways, non-structural |
| M15 | 1:2:4 | 15 MPa | ~320 kg | Lightly loaded slabs, boundary wall footings |
| M20 ★ | 1:1.5:3 | 20 MPa | ~400 kg | Standard RCC — slabs, beams, columns (most used) |
| M25 | 1:1:2 | 25 MPa | ~480 kg | Heavy columns, raft foundations, bridges |
| M30 | 1:0.75:1.5 | 30 MPa | ~540 kg | Pre-stressed, high-rise structures |
| M40+ | Design Mix | 40+ MPa | Lab designed | Bridges, dams, large commercial towers |
★ M20 is the minimum grade for all reinforced concrete (RCC) structural members per Pakistan building regulations and IS 456. Using M15 for structural columns or beams is a serious code violation.
Worked Example — 1000 sq ft Roof Slab (M20 Grade)
Problem: Calculate cement bags, sand, and aggregate for a 1000 sq ft roof slab, 5 inches thick, M20 concrete, 5% wastage.
Given:
Area = 1000 sq ft = 92.9 m²
Thickness = 5 inches = 0.127 m
Grade = M20 (1:1.5:3) → Total parts = 5.5
Wastage = 5%
Step 1: Wet Volume = 92.9 × 0.127 × 1.05 = 12.38 m³
Step 2: Dry Volume = 12.38 × 1.54 = 19.07 m³
Step 3: Cement = (1/5.5) × 19.07 = 3.47 m³
Cement = 3.47 × 1440 = 4,995 kg
Cement = 4,995 ÷ 50 = 100 bags
Step 4: Sand = (1.5/5.5) × 19.07 × 35.31 = 184 cft
Aggregate = (3/5.5) × 19.07 × 35.31 = 368 cft
Step 5: Water = 4,995 × 0.45 = 2,248 litres
ANSWER: 100 bags cement | 184 cft sand | 368 cft aggregate
For a 10-marla house roof (approximately 1,200–1,500 sq ft), expect 120–150 bags of cement for the slab alone. Add beam, column, and footing concrete separately for total project requirements.
Quick Reference — Materials per 1 m³ of Concrete
Use these values for fast estimation without calculation. These are for finished wet concrete — remember to add your wastage percentage on top.
| Grade | Cement (50kg bags) | Sand (cft) | Aggregate (cft) | Water (litres) |
|---|---|---|---|---|
| M10 (1:3:6) | 4.3 bags | 36 cft | 72 cft | ~195 L |
| M15 (1:2:4) | 6.5 bags | 36 cft | 73 cft | ~293 L |
| M20 (1:1.5:3) | 8.1 bags | 34 cft | 68 cft | ~364 L |
| M25 (1:1:2) | 9.5 bags | 27 cft | 54 cft | ~427 L |
| M30 (1:0.75:1.5) | 11.0 bags | 23 cft | 46 cft | ~495 L |
Cement & Aggregate Prices in Pakistan — 2025
Cement Brands & Prices
| Brand | Grade / Type | Price per 50 kg bag | Strength @ 28 days |
|---|---|---|---|
| DG Khan Cement | OPC 43 Grade | PKR 1,250–1,400 | 43 MPa |
| Lucky Cement | OPC 43/53 Grade | PKR 1,200–1,380 | 43–53 MPa |
| Bestway Cement | OPC 43 Grade | PKR 1,200–1,350 | 43 MPa |
| Maple Leaf Cement | OPC 43 Grade | PKR 1,180–1,320 | 43 MPa |
| Fauji Cement | OPC 43 Grade | PKR 1,150–1,300 | 43 MPa |
| Attock Cement | OPC 43 Grade | PKR 1,100–1,250 | 43 MPa |
| Cherat Cement | OPC 43 Grade | PKR 1,100–1,250 | 43 MPa |
Aggregate & Sand Prices
| Material | Specification | Price per cft | Price per m³ |
|---|---|---|---|
| Crush (3/4" aggregate) | RCC grade crushed stone | PKR 80–120 | PKR 2,800–4,200 |
| Crush (1/2" aggregate) | Fine crush for floor work | PKR 90–130 | PKR 3,200–4,600 |
| River Sand (Chenab) | Clean river sand | PKR 40–70 | PKR 1,400–2,500 |
| Crusher Sand (roray) | Stone-crushed fine sand | PKR 50–80 | PKR 1,750–2,800 |
Always check the manufacture date on cement bags — do not use cement older than 3 months as it loses 10–20% strength per month of storage. Buy in batches and store in a dry, elevated area away from moisture.
Expert Tips for Concrete Work in Pakistan
Materials & Preparation
- Never use sea sand or Karachi beach sand — salt content destroys steel reinforcement within 5–10 years causing concrete to crack and spall
- Wash aggregate (crush) if dusty — dust coating reduces cement-aggregate bond strength by up to 30%
- Wet formwork thoroughly before pouring — dry timber absorbs water from fresh concrete, weakening the surface layer
- Verify all rebar positions and cover before pour — minimum cover 25 mm for slabs, 40 mm for columns and beams
Mixing on Site
- Always use a drum mixer — manual mixing reduces strength by 15–20% and is acceptable only for PCC (non-structural) work
- Add water gradually — never pour all water at once as it creates uneven hydration
- Mix for minimum 2 full minutes after all materials are added and water is incorporated
- In summer above 35°C: add crushed ice to mixing water or pour in early morning to prevent premature stiffening
- Pour within 30 minutes of mixing — concrete starts initial set after 45 minutes
Curing — The Most Critical Step
- Begin curing within 2–3 hours after pour — apply wet hessian / gunny bags or polythene sheeting immediately after initial set
- Water-cure continuously for 7 days minimum for M20 and 14 days minimum for M25 and above
- Concrete reaches 70% design strength at 7 days and 99% at 28 days — never apply structural loads before 28 days
- In hot and dry weather (Lahore summers): water the slab surface twice daily morning and evening to prevent plastic shrinkage cracking
Most common site mistake in Pakistan: labourers add extra water on site to make concrete more fluid and easier to pour. This single action reduces concrete strength by 20–40%. If workability is needed, use a chemical plasticizer (superplasticizer additive) — never extra water.
Recommended Slab Thickness — Pakistan Residential Construction
| Slab Type | Span Range | Min Thickness | Concrete Grade |
|---|---|---|---|
| Solid RCC Slab | Up to 3.5 m | 4.5" (115 mm) | M20 minimum |
| Solid RCC Slab | 3.5 m to 5 m | 5–6" (125–150 mm) | M20 |
| Flat Slab (no beams) | 4 m to 7 m | 7–9" (175–225 mm) | M25 |
| Roof Slab (top floor) | Any | 5" minimum (125 mm) | M20 |
| Ground Floor PCC | Any | 4" (100 mm) | M10 or M15 |
| Basement / Raft | Any | 8–12" (200–300 mm) | M25 to M30 |
Values are as per IS 456 and Pakistan standard practice. Final thickness must be confirmed by structural design calculations.
Frequently Asked Questions
For a 1000 sq ft roof slab, 5 inches thick, M20 grade with 5% wastage: approximately 100 bags of cement, 184 cft of river sand, and 368 cft of aggregate (crush). If 6 inches thick: approximately 120 bags. Use the calculator above for your exact dimensions. Always add 5–8% extra for wastage and spillage on site.
When dry cement, sand, and aggregate are mixed together, fine sand particles fill the voids between coarse aggregate particles, and water hydration causes further volume reduction. The final wet concrete volume is approximately 35% less than the sum of the dry material volumes. So to produce 1 m³ of wet concrete, you need 1.54 m³ of dry ingredients (1 ÷ 0.65 ≈ 1.54). This is a universal constant in all concrete calculation codes worldwide — IS 456, ACI 318, BS 8110.
Per IS 456 adopted by Pakistan: minimum grade for all reinforced concrete (RCC) structural members is M20. This applies to slabs, beams, columns, and foundations of all residential and commercial buildings. M15 may only be used for plain cement concrete (PCC) — non-structural uses like ground levelling, pathways, and bedding layers. Using M15 for structural RCC is a serious code violation and safety risk.
Absolutely not. Sea sand contains chloride salts that penetrate concrete and attack steel reinforcement bars, causing severe corrosion and structural failure within 5–15 years. This is a documented problem in Karachi and coastal projects. Mixing water must also be clean and potable. Always insist on certified river sand (Chenab, Ravi, or similar) for structural concrete. Similarly, industrial waste water or brackish groundwater must never be used for mixing.
Volume of a circular column = π/4 × diameter² × height. Example — 300mm diameter, 3m height: Volume = π/4 × 0.3² × 3 = 0.212 m³. Apply wastage: 0.212 × 1.05 = 0.222 m³. Dry Volume = 0.222 × 1.54 = 0.342 m³. For M20 (1:1.5:3): Cement = (1/5.5) × 0.342 × 1440 ÷ 50 = 1.79 bags → 2 bags per column. For 10 columns: 20 bags minimum. Enter the equivalent rectangular dimensions in the calculator above for a close estimate.
Freshly poured concrete timeline: Initial set (no walking) — 4 to 8 hours. Light foot traffic — after 24 hours. Formwork removal (columns/walls) — after 24 to 48 hours. Formwork removal (slab soffit) — after 14 days minimum (21 days for spans over 4.5m). Full structural loading — after 28 days. In cold weather (below 15°C common in Islamabad winters), add 50% to all these times as hydration slows significantly.
