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Concrete Calculator
Find how much concrete to order. Choose a slab, footing or round column, enter the size and thickness, and add a waste allowance. You get cubic yards for a ready-mix truck and the number of 40, 60 or 80 lb bags.
How to use the Concrete Calculator
- Choose the shape.
- Enter length, width (or diameter) and thickness.
- Enter the quantity and waste %.
- Order cubic yards or the number of bags.
Formula
Cubic yards = length × width × thickness (ft) ÷ 27
80 lb bag ≈ 0.6 cu ft · 60 lb ≈ 0.45 · 40 lb ≈ 0.3
Example
A 10 × 10 ft patio, 4 inches thick: 33.3 cu ft = 1.23 cubic yards; with 10% waste about 1.36 yd - 62 bags of 80 lb.
Thickness guide
- Sidewalks and patios: 4 in
- Driveways: 4-6 in
- Garage floors: 5-6 in
- Footings: check local building code
Related free tools
Frequently asked questions
Bags or a truck?
For more than about 1 cubic yard, ready-mix is usually easier and cheaper.
How long until I can walk on it?
Usually 24-48 hours; drive on it after about 7 days.
Do I need rebar?
Driveways and structural slabs usually need rebar or mesh.
What is a short load fee?
Many suppliers charge extra for deliveries under a few yards.
Results are estimates for planning. Your inputs stay in your browser and are not sent to Soft2Cloud.
Last updated: November 2026