Calculate exactly how much concrete you need for any project—driveways, patios, foundations, and more.
Calculating concrete needs is straightforward once you understand the basic formulas for different shapes. Here are the standard methods for common project types:
For example: A 20 ft long, 10 ft wide driveway with 4 inches of concrete requires (20 × 10 × 0.333) ÷ 27 = 2.47 cubic yards
Measure the perimeter length, width of the footing, and depth below ground. A 100 ft perimeter, 2 ft wide, 3 ft deep footing requires (100 × 2 × 3) ÷ 27 = 22.2 cubic yards
For a 1 ft diameter post hole, 4 ft deep: (3.14159 × 0.5² × 4) ÷ 27 = 0.12 cubic yards
Concrete stairs volume is the width multiplied by half the rise-run product multiplied by the number of steps, then divided by 27 for cubic yards. This accounts for the tapered wedge shape of each step.
Bagged concrete is perfect for small to medium projects and post holes. One cubic yard equals approximately:
Our calculator uses industry-standard formulas and automatically includes a 10% waste overage. Here's how the math works for each project type:
Project: 20 ft × 15 ft driveway, 4 inches thick
The 10% overage accounts for measurement variations, uneven surfaces, spillage, and settling during the pour. It's always better to have slightly extra than to run short mid-project.
Different projects call for different concrete mixes. Here's a comparison of common types:
| Type | Strength (PSI) | Best For | Cost Per Yard | Setting Time |
|---|---|---|---|---|
| Standard Concrete | 4,000 | Driveways, patios, foundations | $125-$150 | 24-48 hours |
| High-Strength | 5,000+ | Commercial, heavy loads, thin sections | $150-$175 | 24-36 hours |
| Fast-Setting | 3,500 | Quick projects, cold weather, repairs | $140-$165 | 6-8 hours |
| Fiber-Reinforced | 4,000 | Crack prevention, decorative finishes | $160-$190 | 24-48 hours |
| Stamped/Colored | 4,000 | Decorative patios, driveways, accents | $175-$225 | 24-48 hours |