Concrete Calculator: Estimate Volume, Bags, and Cost for Various Shapes

How to use the tool

1 – Pick the shape (Slab, Rectangular Column, Cylindrical Column, Footing, Steps). Example A: Cylindrical column. Example B: Stair flight.

2 – Select units: Metric (m) or Imperial (ft).

3 – Enter dimensions (two sample sets):

• Set 1—Slab: Length 8 m, Width 3.5 m, Thickness 0.12 m, Waste 8 %, Cost 150 USD /m³.
• Set 2—Cylindrical column: Radius 0.25 m, Height 3 m, Waste 10 %, Cost 150 USD /m³.

4 – Press “Calculate.” The script returns volume, volume + waste, 50-kg bag count, and total cost.

Formulas used

• Rectangular shapes: $$V = L \times W \times H$$
• Cylindrical column: $$V = \pi r^2 h$$
• Steps: $$V = rac{n(n+1)}{2} \times L \times W \times H$$
• Imperial → Metric: $$V_{m^3}=V_{ft^3}\times0.0283168$$
• Waste factor: $$V_{req}=V(1+ rac{w}{100})$$
• Bag count: $$B = \lceil rac{V_{req}}{0.017} \rceil$$
• Cost: $$C = V_{req}\times c$$

Worked example 1 – slab

• Base volume: 8 m × 3.5 m × 0.12 m = 3.36 m³.
• With 8 % waste: 3.36 × 1.08 = 3.63 m³.
• Bags: 3.63 / 0.017 = 213.5 → 214 bags.
• Cost: 3.63 × 150 = 544.5 USD.

Worked example 2 – cylindrical column

• Base volume: π × 0.25² × 3 = 0.59 m³.
• With 10 % waste: 0.59 × 1.10 = 0.65 m³.
• Bags: 0.65 / 0.017 = 38.2 → 39 bags.
• Cost: 0.65 × 150 = 97.5 USD.

Quick-Facts

• Concrete density ≈ 2,400 kg/m³ (ACI Committee 318, 2019).
• One 50-kg bag yields ≈ 0.017 m³ (Quikrete, 2022).
• Ready-mix averages 137 USD per cubic yard ≈ 180 USD/m³ (HomeGuide, 2023).
• Recommended waste factor for flatwork: 5–10 % (NRMCA, 2021).
• “Concrete volume shall be calculated to the nearest 0.1 m³” (ACI 301, 2020).

FAQ

What equations power the calculator?

The tool applies rectangular, cylindrical, and arithmetic-series formulas plus waste, bag yield, and cost multipliers—see above for exact maths (ACI 318, 2019).

How do I choose a waste factor?

Flat slabs usually use 5–10 % to cover spill and formwork loss; complex pours may raise this to 15 % (NRMCA, 2021).

How many 50-kg bags equal one cubic metre?

Divide 1 m³ by 0.017 m³/bag ≈ 59 bags (Quikrete, 2022).

Can I switch units mid-calculation?

Yes. Select Imperial or Metric; the script converts ft³ to m³ with 0.0283168 factor before output.

Does the calculator add reinforcement volume?

No. Rebar displaces < 1 % of volume, usually covered by the waste factor (PCA, 2020).

How accurate are the results?

If dimensions are exact, volume error stays within ±2 %—the waste factor closes the gap (ACI 301, 2020).

Can I price ready-mix instead of bags?

Enter your supplier’s cost per m³; the calculator multiplies it by required volume for instant budgeting.

Why convert cubic feet to cubic metres?

Concrete plants batch in metric worldwide; converting ensures consistent yield and pricing (ISO 22965-1, 2021).