Concrete Calculator – Volume, Cement, Sand & Aggregate Estimator
Use this free concrete calculator to find out exactly how much concrete you need for slabs, columns, footings, beams, stairs or curb work. Enter dimensions in feet/inch or meter/cm, choose your concrete grade, and get concrete volume, cement bags, sand, aggregate, water, truck loads and material cost — with step-by-step working.
🏗️ Concrete Calculator
Volume + cement, sand, aggregate & water — with step-by-step working
Slab / Wall / Footing
Round Column / Footing
Circular Slab
Beam
Stairs
Curb & Gutter
📋 Calculation Details (step-by-step)
Includes 5% wastage. 1 bag = 50 kg = 1.25 cft. Verify with your site engineer.
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Concrete Material Rates by Country (2026)
Live concrete material rates — select your currency, enter local market rates, and the per-cft / per-cubic-meter cost for each grade recalculates automatically. Material cost only; labour, shuttering, steel and transport are extra.
💰 Concrete Material Rates
| Grade (Mix) | Rs / cft | Rs / cubic meter |
|---|---|---|
| M15 (1:2:4) — PCC, footings | — | — |
| M20 (1:1.5:3) — slabs, beams, columns | — | — |
| M25 (1:1:2) — heavy structural | — | — |
Default values are 2026 market midpoints for Lahore/Punjab, Pakistan. Changing the currency loads example rates for that currency — please replace them with your actual local market rates. Ready-mix (plant) concrete typically costs more per m³ than site mixing because it includes batching, transport and quality control. Figures are material cost only and exclude labour, formwork, steel and pumping.
Related Construction Calculators
Planning a full project? Try our other free construction calculators — estimate bricks, cement, sand, plaster, tiles, paint and water tank capacity with the same step-by-step working. Every concrete estimate pairs well with our cement calculator for mortar and plaster work.
Frequently Asked Questions
What is the "dry volume factor" of 1.57?
Wet concrete occupies less volume than its dry ingredients measured separately, because fine particles fill the voids between coarse aggregate. Multiplying wet volume by 1.57 gives the total dry volume of cement + sand + aggregate you must purchase. This is the standard factor used by site engineers in Pakistan and India.
How many cement bags are in 1 cubic meter of M20 concrete?
For M20 (1:1.5:3): dry volume = 1 × 1.57 = 1.57 m³. Cement = 1.57 × 1/5.5 = 0.285 m³. One 50 kg bag = 0.0354 m³, so about 8 bags per cubic meter before wastage. The calculator does this math for your exact dimensions.
Why does the calculator round cement bags up?
You cannot buy a fraction of a bag, so the result is always rounded up to the next whole bag. The same ceiling rule applies to ready-mix trucks. Sand and aggregate are shown with one decimal since they are sold loose.
What water-cement ratio is assumed?
0.5 — meaning half a liter of water per kg of cement. This is a practical average for site-mixed concrete. Actual water needed varies with aggregate moisture and weather; always adjust on site for workability and follow your engineer's mix design for structural concrete.
How do I enter 10 feet 6 inches?
Select "Feet / Inch", then enter 10 in the feet box and 6 in the inch box of that dimension. The calculator combines them automatically (10.5 ft).
What is the "waist slab" in the stairs calculation?
The waist is the sloped concrete slab under the steps that carries the load. The calculator adds triangular steps plus the waist slab along the slope. Default waist thickness is 6 inches — increase it for longer spans as per your structural drawing.
Which grade should I select — M15, M20 or M25?
M15 (1:2:4) is used for PCC, footings and non-structural work. M20 (1:1.5:3) is the standard for slabs, beams and columns in residential construction. M25 (1:1:2) is for heavier structural work. When in doubt, follow your structural drawings, not this calculator.
Why is wastage set to 5% by default?
Some concrete always sticks to the mixer, spills during pouring, or overfills formwork. 5% is a normal site allowance. Increase it to 7–10% for complex shapes like stairs or when formwork is uneven.
How big is a ready-mix truck?
The calculator assumes a standard 6 cubic meter transit mixer, common in Pakistan. If your supplier uses a different size, divide your cubic meters by their truck capacity.
How do I use the currency selector in the rates table?
Pick your currency from the dropdown — example material rates for that currency load automatically. Then replace them with your actual local market rates (cement per bag, sand and crush per cft). The per-cft and per-cubic-meter cost for M15, M20 and M25 recalculates instantly in your currency.
Does this include steel reinforcement?
No — this calculator covers concrete materials only (cement, sand, aggregate, water). Steel is calculated separately with a Bar Bending Schedule.
How to Use This Concrete Calculator
- Select the member shape — Slab/Wall/Footing, Round Column/Footing, Circular Slab, Beam, Stairs, or Curb & Gutter. Each shape asks only for the dimensions it needs.
- Choose the unit system — Feet/Inch or Meter/CM, whichever your drawings use.
- Pick the concrete grade — M15 (1:2:4), M20 (1:1.5:3), M25 (1:1:2), or enter a custom cement:sand:aggregate ratio.
- Set the number of members — e.g. 4 identical columns; the concrete calculator multiplies automatically.
- Set wastage % — 5% is standard for formed work; use 7–10% for stairs and irregular shapes where spillage is higher.
- Press Calculate Concrete — wet volume, cement bags, sand, aggregate, water, and truck loads appear with full step-by-step working.
Concrete Calculation Formula (How the Calculator Works)
This concrete calculator uses the dry volume method — the standard site procedure across Pakistan:
- Step 1 — Wet volume: the actual volume of the member. Slab: length × width × thickness. Round column: (π/4) × diameter² × height.
- Step 2 — Dry volume: wet volume × 1.52. (Concrete shrinks when water is added and voids fill, so dry materials occupy about 52% more volume than the finished concrete.)
- Step 3 — Split by ratio: for M20 (1:1.5:3), total parts = 5.5. Cement = dry volume × 1/5.5; sand = dry volume × 1.5/5.5; aggregate = dry volume × 3/5.5.
- Step 4 — Convert cement to bags: 1 bag = 50 kg = 1.25 cubic feet. Bags = cement volume ÷ 1.25.
- Step 5 — Add wastage on top of all quantities.
Example: 100 cft of M20 → dry volume = 152 cft → cement = 152/5.5 = 27.6 cft → 27.6 ÷ 1.25 = 22 bags; sand = 41.4 cft; aggregate = 82.9 cft (before wastage).
Volume Formulas by Member Type
| Member | Formula (wet volume) |
|---|---|
| Slab / wall / footing (rectangular) | Length × Width × Thickness |
| Round column / footing | (π/4) × Diameter² × Height |
| Circular slab | (π/4) × Diameter² × Thickness |
| Beam | Length × Breadth × Depth |
| Stairs | (Tread × Rise × Width × Steps ÷ 2) + waist-slab volume |
| Curb & gutter | Length × Cross-section area |
Practical note: For stairs, the triangular steps plus the waist slab (the sloped slab under the steps) must both be counted — beginners often forget the waist slab and run short by 30–40%.
Materials per 100 Cft of Concrete (Ready Reference)
| Grade | Ratio | Cement bags (50 kg) | Sand (cft) | Aggregate (cft) | Water (litres, approx) |
|---|---|---|---|---|---|
| M15 | 1:2:4 | ~15 | ~41 | ~83 | ~375 |
| M20 | 1:1.5:3 | ~22 | ~41 | ~83 | ~550 |
| M25 | 1:1:2 | ~30 | ~38 | ~76 | ~750 |
(Approximate, before wastage. Water assumes w/c ≈ 0.5 — see below. The concrete calculator above gives exact figures for any volume.)
Water-Cement Ratio: Why It Matters
Water is not "as needed" — the water-cement ratio (w/c) decides strength:
| Grade | Maximum w/c (IS 456, moderate exposure) |
|---|---|
| M15 | 0.60 |
| M20 | 0.55 |
| M25 | 0.50 |
More water than this makes concrete easier to place but permanently weaker and more porous. On site, measure water (a marked drum beats a hose pipe), especially in hot weather when the temptation to add "thoda aur pani" is strongest. I have seen 28-day cube failures traced to nothing but an unmeasured hose.
Worked Example: 4 Round Columns
Data: 4 columns, 12-inch (1 ft) diameter, 10 ft height, M20 concrete, 5% wastage.
- Wet volume per column = (π/4) × 1² × 10 = 7.85 cft; × 4 columns = 31.4 cft
- Dry volume = 31.4 × 1.52 = 47.7 cft
- Cement = 47.7 ÷ 5.5 = 8.67 cft → 8.67 ÷ 1.25 = 6.9 bags → with 5% wastage ≈ 7.3 bags (order 8)
- Sand = 47.7 × 1.5/5.5 = 13.0 cft → 13.7 cft with wastage
- Aggregate = 47.7 × 3/5.5 = 26.0 cft → 27.3 cft with wastage
Practical note: Always round cement UP to whole bags when ordering — a half-bag shortage stops a pour, while one extra bag costs little and stores for the next work.
Ready-Mix Truck Loads
One transit mixer carries about 6 m³ (≈ 212 cft) of concrete. The concrete calculator converts your total volume into truck loads automatically — but remember: order the last truck slightly light and top up with site-mixed concrete if needed, because returning a half-empty mixer still costs nearly full price.
Frequently Asked Questions
How much concrete do I need for a 10 × 10 ft slab, 6 inches thick?
Wet volume = 10 × 10 × 0.5 = 50 cft. For M20: dry volume = 76 cft → cement = 76/5.5 = 13.8 cft = 11 bags; sand ≈ 20.7 cft; aggregate ≈ 41.5 cft (before 5% wastage). The calculator above does this instantly for any size.
What is the difference between wet volume and dry volume?
Wet volume is the finished concrete in the member. Dry volume is the loose bulk of cement + sand + aggregate before water is added — about 52% more, because water fills voids and the mix compacts. All material estimates start from dry volume.
Why multiply by 1.52?
It is the standard bulking-and-shrinkage factor used in Pakistani/Indian site practice (range 1.52–1.57). It accounts for voids between aggregate particles that cement paste fills, plus handling losses. The factor is approximate — hence the separate wastage % setting.
Which grade should I use — M15, M20, or M25?
M15 (1:2:4) for PCC, footings base, and non-structural work; M20 (1:1.5:3) for slabs, beams, and columns in normal buildings; M25 (1:1:2) for heavier frames and where the structural drawings demand it. Always follow the drawings — the grade is the designer's call, not the calculator's.
How much water does concrete need?
Roughly w/c × cement weight. For M20 at w/c 0.5: 22 bags × 50 kg = 1100 kg cement → ~550 litres per 100 cft of concrete. Never exceed the w/c limit for your grade and exposure — extra water permanently cuts strength.
How many bags in one cubic meter of M20?
1 m³ = 35.31 cft → dry volume = 53.7 cft → cement = 9.76 cft = 7.8 bags (≈ 8 bags with wastage).
Can I use this concrete calculator for columns and footings too?
Yes — select Round Column/Footing or the rectangular option and enter the dimensions. For footings, remember the PCC base layer (usually M15, 3–4 inches) is estimated separately.
What wastage % should I set?
5% for formed slabs, beams, and columns; 7–10% for stairs, curb work, and anything hand-mixed or placed in awkward shapes. When in doubt, the higher value is cheaper than a stopped pour.
Written by Mohsin Raza Adil — BSc Civil Engineering Technologist (NTC-registered), Pakistan.