🏗️ 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:

Length (ft) Slab or footing length

Width (ft) Slab or footing width

Depth / Thickness (inches) Slab: 4–6 in · Beam depth in inches

Concrete Grade (Mix Ratio)

Wastage (%) Recommended: 5–8%

Number of Elements 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.

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.

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.

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.

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.

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.