Concrete Calculator
Ordering the right amount of concrete is critical for any construction project. Too little means a second pour with an ugly cold joint; too much is wasted money. This calculator takes your slab dimensions (length, width, and depth) and computes the exact volume in cubic feet, cubic yards, and equivalent pre-mixed bags, including an adjustable waste factor.
The calculation is straightforward: Volume = Length × Width × Depth
The depth is entered in inches and automatically converted to feet. Results include:
- Cubic yards — what you order from a ready-mix supplier (trucks typically carry 8-10 yd³)
- 60-lb bags — each yields approximately 0.45 ft³ of mixed concrete
- 80-lb bags — each yields approximately 0.60 ft³ of mixed concrete
Standard concrete depth recommendations:
- Sidewalks and patios: 4 inches
- Driveways (cars): 4-6 inches
- Driveways (heavy vehicles): 6-8 inches
- Garage floors: 4-6 inches
- Footings: 8-12 inches or per local code
The waste factor (default 10%) accounts for uneven subgrade, spillage, and over-excavation. For well-prepared sites, 5% is reasonable; for irregular shapes or first-time DIY, consider 10-15%.