Concrete Volume Calculator
Estimate cubic yards for slabs, footings & columns โ trusted by pros
standard driveway: 4″โ6″
๐ฆ Estimated Concrete Needed
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โ ๏ธ Disclaimer: Always consult a structural engineer for load-bearing elements. This tool provides estimates only.
๐ How to Use This Concrete Calculator (Step-by-Step)
Follow these simple steps to get an accurate estimate of concrete volume for your project:
- Select your shape โ Choose between Slab/Pad, Rectangular Footing, or Round Column.
- Enter dimensions โ Length, width, thickness (slab) / length, width, depth (footing) / diameter, height (column).
- Click “Calculate” โ The tool instantly computes cubic yards, cubic feet, and bag estimates.
- Add extra for waste โ Our calculation already includes 5% waste. For complex shapes, add 10%.
- Order your concrete โ Use the cubic yards figure to order from your ready-mix supplier.
Pro tip: Always round up to the nearest quarter yard when ordering. Most suppliers have a minimum delivery fee, so consolidate orders when possible.
๐๏ธ Real-World Examples
Example 1: Driveway Slab
Dimensions: 40 ft long ร 12 ft wide ร 5 inches thick
Raw volume: 40 ร 12 ร (5/12) = 200 cu ft
With 5% waste: 210 cu ft = 7.8 cubic yards
Bags needed: 350 x 80lb bags OR 467 x 60lb bags
Dimensions: 40 ft long ร 12 ft wide ร 5 inches thick
Raw volume: 40 ร 12 ร (5/12) = 200 cu ft
With 5% waste: 210 cu ft = 7.8 cubic yards
Bags needed: 350 x 80lb bags OR 467 x 60lb bags
Example 2: House Foundation Footing
Dimensions: 80 ft long ร 16 inches wide ร 12 inches deep
Raw volume: 80 ร (16/12) ร (12/12) = 106.7 cu ft
With 5% waste: 112 cu ft = 4.2 cubic yards
Dimensions: 80 ft long ร 16 inches wide ร 12 inches deep
Raw volume: 80 ร (16/12) ร (12/12) = 106.7 cu ft
With 5% waste: 112 cu ft = 4.2 cubic yards
Example 3: Deck Support Column
Dimensions: 10 inches diameter ร 6 ft height
Raw volume: ฯ ร (5/12)ยฒ ร 6 = 3.27 cu ft
With 5% waste: 3.4 cu ft = 0.13 cubic yards (about 6 x 80lb bags)
Dimensions: 10 inches diameter ร 6 ft height
Raw volume: ฯ ร (5/12)ยฒ ร 6 = 3.27 cu ft
With 5% waste: 3.4 cu ft = 0.13 cubic yards (about 6 x 80lb bags)
Example 4: Patio with Irregular Shape
Tip: Break irregular areas into rectangles, calculate each, then sum the volumes.
Example: L-shaped patio = 20ร10 slab + 8ร6 slab, both 4″ thick โ 2.47 + 0.59 = 3.06 cubic yards
Tip: Break irregular areas into rectangles, calculate each, then sum the volumes.
Example: L-shaped patio = 20ร10 slab + 8ร6 slab, both 4″ thick โ 2.47 + 0.59 = 3.06 cubic yards
โ Frequently Asked Questions
How much concrete do I need for a 10×10 slab?
For a 10ร10 slab at 4 inches thick: 10ร10ร(4/12) = 33.33 cu ft รท 27 = 1.23 cubic yards. With 5% waste, order 1.3 cubic yards or about 55 x 80lb bags.
What’s the difference between a slab and a footing?
A slab is a flat, horizontal surface (patio, driveway, floor). A footing is a wider base that supports walls or columns, typically buried below frost line. Footings require deeper excavation and often rebar reinforcement.
How much waste should I account for?
We include 5% waste in our calculation. For complex shapes, multiple pours, or difficult site access, increase to 10%. For large projects (20+ yards), order 10-15% extra to avoid running short.
How many 80lb bags are in a cubic yard?
One cubic yard = 27 cubic feet. An 80lb bag yields approx 0.6 cubic feet, so you need 45 bags per cubic yard (27 รท 0.6 = 45). A 60lb bag yields 0.45 cu ft, requiring 60 bags per yard.
Should I use bags or ready-mix truck?
For under 1 cubic yard (about 45 bags), bags are practical. For larger pours, ready-mix is cheaper, more consistent, and saves labor. Most trucks charge a short-load fee under 5-7 yards.
Does this calculator account for rebar or forms?
No. This calculator estimates concrete volume only. Reinforcement steel (rebar/mesh) and formwork (wood/metal molds) are separate costs and materials. For structural elements, consult an engineer.
