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Concrete Calculator

Calculate the volume of concrete needed for slabs, columns, and footings, plus the number of bags required.

Concrete Required

About the Concrete Calculator

The Oneyfy Concrete Calculator helps contractors, builders, and DIY enthusiasts quickly determine how much concrete they need for a project. It calculates volume in cubic yards and cubic feet, and tells you how many pre-mixed bags to purchase.

How to Use

  1. Select your Project Type: Rectangular Slab, Circular Column, or Stair Steps.
  2. Select your preferred unit of measurement (feet or meters).
  3. Enter the dimensions for your shape.
  4. Click Calculate to see volume and bags needed.

How It Works

Slab: Volume (ft³) = Length × Width × Depth. Convert to cubic yards: ÷ 27.

Column: Volume (ft³) = π × (diameter/2)² × height.

Bags: A 60 lb bag yields ~0.45 cubic feet; an 80 lb bag yields ~0.60 cubic feet.

A 10% waste factor is automatically added to bag estimates.

Example

A 10×10 ft slab, 4 inches (0.333 ft) thick: Volume = 33.3 ft³ = 1.23 cubic yards. You need approximately 82 × 60 lb bags or 62 × 80 lb bags.

Frequently Asked Questions

Divide inches by 12. Common depths: 4 inches = 0.333 ft, 6 inches = 0.5 ft, 8 inches = 0.667 ft.
Yes. It's standard practice to order 5–10% extra to account for spillage, uneven ground, and minor miscalculations. The bag estimate already includes a 10% waste factor.
A standard concrete mixer truck holds 8–10 cubic yards. If your project exceeds 1–2 cubic yards, ready-mix delivery may be more economical than bagged concrete.
A 60 lb bag yields approximately 0.45 cubic feet; an 80 lb bag yields approximately 0.60 cubic feet. 80 lb bags are more cost-effective but heavier to handle.