Concrete Volume Calculator
Estimate concrete volume for slabs, footings, and columns.
Concrete Volume Calculator
What This Calculator Does
The Concrete Volume Calculator quickly converts your slab's square footage and thickness to cubic yards of concrete needed, plus the number of 60-lb and 80-lb premix bags. Enter the length, width, and thickness in inches, and get the concrete volume in the units your supplier needs.
Whether you're pouring a patio, driveway, sidewalk, or foundation, concrete volume must be calculated before ordering. Ready-mix concrete is ordered by the cubic yard. Bagged concrete (60-lb or 80-lb sacks) is sold in bags - knowing both numbers lets you compare the cost of mixing your own vs. ordering a delivered mix. A 60-lb bag yields approximately 0.45 cubic feet; an 80-lb bag yields 0.60 cubic feet.
This calculator is optimized for slab-on-grade pours: patios, driveways, garage floors, sidewalks, and shed slabs. For walls, footings, or columns, use our main Concrete Calculator which supports more geometries.
How to Use
- Measure the length and width of the pour area in feet.
- Determine the slab thickness in inches (standard: 4 in for patios and sidewalks, 5-6 in for driveways).
- Enter all dimensions into the calculator fields above.
- Click "Calculate" to see cubic yards, 60-lb bags, and 80-lb bags needed.
- Compare the cost: bagged concrete vs. ready-mix delivery for your project size.
Worked Examples
Sidewalk Section
A 4 ft wide by 30 ft long sidewalk section poured at 4 inches thick with standard 3,000 PSI mix.
- →Area: 4 ft x 30 ft = 120 sq ft.
- →Thickness in feet: 4 in / 12 = 0.333 ft.
- →Cubic feet: 120 x 0.333 = 40 cu ft.
- →Cubic yards: 40 / 27 = 1.48 cu yd.
- →With 10% waste: 1.48 x 1.10 = 1.63 cu yd (order 1.75 cubic yards).
- →Bagged equivalent: 1.48 cu yd x 45 bags = 67 bags of 80-lb mix.
Result: Approximately 1.5 cubic yards of concrete needed; order 1.75 cubic yards for waste. Bagged option would require 67 bags of 80-lb mix.
Sidewalks need control joints every 4-5 ft to prevent random cracking. Cut joints within 6-12 hours after finishing for best results.
Reference Table
| Slab Size | Thickness | Cubic Yards | 60-lb Bags | 80-lb Bags |
|---|---|---|---|---|
| 10 x 10 ft | 4 in | 1.23 | 55 bags | 45 bags |
| 10 x 10 ft | 6 in | 1.85 | 83 bags | 68 bags |
| 12 x 12 ft | 4 in | 1.78 | 80 bags | 66 bags |
| 20 x 20 ft | 4 in | 4.94 | 222 bags | 183 bags |
| 20 x 20 ft | 5 in | 6.17 | 278 bags | 228 bags |
| 24 x 24 ft | 4 in | 7.11 | 320 bags | 263 bags |
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