Cement Calculator — Bags for Concrete & Mortar
1 bag = 50 kg = 1.25 cu ft. Includes 5% wastage.
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Related Construction Calculators
Need concrete for your project? Try our free Concrete Calculator — estimate concrete volume, cement bags, sand, aggregate, water and material cost for slabs, columns, beams, stairs and footings, with step-by-step working.
How to Use This Cement Calculator
- Select work type — Concrete (slab, beam, column, footing) or Mortar (brickwork, plaster).
- Pick the grade/ratio — M15 (1:2:4), M20 (1:1.5:3), or M25 (1:1:2) for concrete; 1:4 or 1:6 for mortar.
- Enter volume in cubic feet — measure length × width × thickness of your element.
- Set wastage % — 5% is standard; use 7–10% for plaster and brickwork where spillage is higher.
- Press Calculate Cement — the cement calculator shows bags, sand, aggregate, and kg instantly.
Cement Calculation Formula (How the Calculator Works)
This cement calculator uses the dry volume method trusted on sites across Pakistan:
- Step 1: Wet volume (your input) × 1.52 = dry volume.
- Step 2: Cement volume = dry volume × cement parts ÷ total parts. For M20 (1:1.5:3): 1 ÷ 5.5.
- Step 3: Convert to bags — 1 bag = 50 kg = 1.25 cubic feet.
- Step 4: Add your wastage percentage on top.
Example: 100 cft of M20 concrete → dry volume = 152 cft → cement = 152 × (1/5.5) = 27.6 cft → 27.6 ÷ 1.25 = 22 bags (before wastage).
Cement Bags Required per 100 Cft of Concrete
| Grade | Ratio | Cement bags (50 kg) | Sand (cft) | Aggregate (cft) |
|---|---|---|---|---|
| M15 | 1:2:4 | ~15 bags | ~41 | ~83 |
| M20 | 1:1.5:3 | ~22 bags | ~41 | ~83 |
| M25 | 1:1:2 | ~30 bags | ~38 | ~76 |
Cement for Mortar (Brickwork & Plaster)
| Mortar ratio | Use | Cement per 100 cft of mortar |
|---|---|---|
| 1:4 | Rich mortar — plaster, waterproofing | ~30 bags |
| 1:6 | Standard brickwork mortar | ~22 bags |
Worked Example: 10 × 10 ft Slab, 6 inches Thick
- Volume = 10 × 10 × 0.5 = 50 cft, grade M20, 5% wastage.
- Enter 50 in the cement calculator → result: ~12 bags of cement, ~21 cft sand, ~43 cft aggregate.
- On site, order 13 bags — one spare bag is cheaper than a stalled pour.
How Much Wastage Should You Add?
- Concrete (machine mixed): 3–5%
- Hand-mixed concrete: 5–7%
- Brickwork: 7–10% (mortar drops, joints)
- Plaster: 10–12% (rebound and spillage)
Frequently Asked Questions
How many cement bags are in 1 cubic meter of M20 concrete?
About 8 bags per cubic meter (M20 needs roughly 320 kg of cement per m³, and each bag is 50 kg).
What is the dry volume factor in cement calculation?
1.52 for concrete and about 1.30 for mortar. It accounts for the voids between sand and aggregate particles.
How many bags of cement per cubic foot?
One 50 kg bag occupies 1.25 cubic feet. Divide any cement volume in cft by 1.25 to get bags.
Which grade of concrete needs the most cement?
Higher grades need more cement: M25 (1:1:2) needs roughly double the cement of M15 (1:2:4) for the same volume.
Does this cement calculator work for plaster?
Yes — select “Mortar”, choose 1:4 or 1:6, enter the plaster volume (wall area × thickness), and add 10% wastage.
Why does my site always run short of cement?
Three usual reasons: no wastage in the estimate, bulking of moist sand, and spillage during hand mixing.
What is the weight of 1 bag of cement in kg?
Standard bag = 50 kg in Pakistan (1.25 cft by volume).
Can I use this cement calculator for a footing or column?
Yes — any concrete element. Calculate its volume (length × width × depth) in cubic feet and enter it.
Related: Concrete Calculator — full material + cost estimate. Brick Calculator — bricks, cement and sand for any wall.