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Concrete Calculator

Calculate concrete volume and material requirements for your project

📦Bag Coverage

40 lb~0.011 yd³
60 lb~0.017 yd³
80 lb~0.022 yd³

📏Common Thickness

Sidewalk4 inches
Driveway4-6 inches
Patio4 inches
Garage6 inches

💡Construction Tips

• Order 5-10% extra material
• Consider delivery costs in budget
• Check local building codes
• Use proper reinforcement (rebar)

Concrete Calculator Guide

A concrete calculator converts dimensions into volume (cubic yards/meters) so you can order enough mix with appropriate waste. Enter length, width, and thickness for slabs—and use shape options for footings, columns, and tubes.

What is Concrete Calculator?

The concrete calculator estimates ready-mix orders or bag counts for DIY projects. It supports unit conversions (in/ft/m, yd^3/m^3) and adds a configurable waste allowance.

How to Use the Concrete Calculator

  1. Choose a shape: slab, footing, column/tube, wall, or step.
  2. Enter dimensions in consistent units (e.g., inches for thickness).
  3. Compute volume in cubic feet and convert to cubic yards/meters.
  4. Add waste (5-10% typical) to account for spillage and over-excavation.
  5. Optionally estimate bag counts by common bag sizes.

Formulas & Methods

  • Slab: V = L * W * H (use feet; H in feet = inches / 12)
  • Cylinder (sonotube/column): V = pi*r^2 * H
  • Footing (rectangular): V = L * W * H (sum segments)
  • Unit conversion: 1 yd^3 = 27 ft^3; 1 m^3 ~ 35.3147 ft^3
  • Bag yields (approx): 40 lb ~ 0.30 ft^3, 60 lb ~ 0.45 ft^3, 80 lb ~ 0.60 ft^3

Assumptions & limitations

  • Dimensions are internal form dimensions; rough ground increases waste.
  • Mix design (PSI/MPa), slump, and admixtures do not affect volume but matter for performance—follow specs.

Examples

Example A — 10x12 ft patio, 4 in thick
Thickness H = 4 in = 0.333 ft. Volume V = 10 * 12 * 0.333 = 39.96 ft^3.
Cubic yards = 39.96 / 27 = 1.48 yd^3. With 10% waste -> 1.63 yd^3 order.

Example B — 12 in diameter pier, 8 ft tall (4 piers)
Radius r = 6 in = 0.5 ft. Single pier V = pi * 0.5^2 * 8 ~ 6.28 ft^3.
Four piers -> ~25.1 ft^3 -> 0.93 yd^3. Add waste as needed.

| Bag Size | Yield (ft^3) | Bags per yd^3 (approx) | |---|---:|---:| | 40 lb | 0.30 | 90 | | 60 lb | 0.45 | 60 | | 80 lb | 0.60 | 45 |

Pro Tips & Best Practices

  • Round up orders; short loads incur extra fees and delays.
  • Keep units consistent—convert thickness to feet before multiplying.
  • Order pumpable mixes for hard-to-reach forms.
  • Place and finish promptly; hot/cold weather affects set time.
  • Follow control joint spacing and curing practices.

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FAQ

Q: How do I calculate concrete volume?

A: Use shape formulas (slab: LWH). Convert cubic feet to cubic yards by dividing by 27.

Q: How much waste should I add?

A: Typically 5-10% for simple forms, 10-15% for complex shapes or manual mixing.

Q: How many bags do I need?

A: Approx yields: 40-lb ~ 0.30 ft^3, 60-lb ~ 0.45 ft^3, 80-lb ~ 0.60 ft^3 per bag; check your brand.

Q: What about rebar or fiber?

A: Reinforcement does not change volume materially but affects mix selection and placement.

Q: How thick should a slab be?

A: Common residential slabs are 4 in thick; follow engineer/contractor specs for your application.

Engineering note: US customary units shown with metric conversions where relevant. Always follow local code/engineer specifications.

Call to Action

Enter your dimensions and waste factor to size the order—then print the volume summary for the batch plant or store.