Concrete Calculator Calculator USA 2026
Calculate the exact volume of ready-mix concrete you need for slabs, footings, driveways and pads in cubic yards, cubic meters and 60/80 lb bags.
Enter your measurements
Results
Volume
133.3 ft³
3.78 m³
Cubic yards (with 10% waste)
5.43 yd³
60 lb bags needed
326
80 lb bags needed
245
Calculation steps
- 1.Volume = 20 × 20 × (4 ÷ 12) = 133.33 ft³
- 2.Cubic yards = 133.33 ÷ 27 = 4.94 yd³
- 3.With 10% waste = 4.94 × 1.10 = 5.43 yd³
- 4.80 lb bags = ⌈5.43 × 45⌉ = 245
Includes a standard waste allowance. Verify with your supplier before ordering.
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Disclaimer: Estimates based on 2026 RSMeans USA data. Actual quantities vary by site conditions, waste and installer practices. Verify with your supplier or contractor before ordering.
How it works
- 1Enter length and width of the pour in feet.
- 2Enter thickness in inches (4" is standard for a patio, 6" for a driveway).
- 3We convert to cubic yards, add a 10% waste allowance, and estimate 60 lb and 80 lb bag counts.
Formula
Worked example
A 20 ft × 20 ft × 4 in patio = 400 × 0.333 = 133.3 ft³ = 4.94 yd³. With 10% waste ≈ 5.43 yd³.
Frequently asked questions
How much waste should I add?
10% is standard for slabs; 15% for uneven ground or complex forms.
How many 80 lb bags per cubic yard?
About 45 bags of 80 lb pre-mix per cubic yard.
What thickness for a driveway?
6 inches for cars, 8 inches for heavy vehicles.