Concrete Volume Calculator
Calculate how much concrete you need in cubic yards or cubic meters.
Enter length, width, and depth to get accurate concrete volume estimates.
Concrete volume is calculated in cubic yards (US) or cubic meters (metric). Concrete is ordered from ready-mix plants by the cubic yard — knowing the exact volume prevents costly over-ordering or having to order a second load mid-pour.
Volume Formula:
Volume (cu ft) = Length × Width × Thickness Cubic Yards = Volume (cu ft) / 27
Worked example — 4-inch driveway slab: Driveway: 40 ft × 16 ft × 4 in (0.333 ft) Volume = 40 × 16 × 0.333 = 213.3 cu ft Cubic yards = 213.3 / 27 = 7.9 cu yd → order 8.5 cu yd (add 8% waste)
Standard slab thickness by application:
| Use | Thickness |
|---|---|
| Sidewalk / patio | 4 inches |
| Residential driveway | 4–5 inches |
| Garage floor | 5–6 inches |
| Commercial driveway | 6 inches |
| Structural slab | 6+ inches (engineer specified) |
Concrete mix ratios (by volume, cement:sand:gravel):
- General purpose: 1:2:3 (2,500 PSI)
- Driveways and slabs: 1:1.5:2.5 (3,500 PSI)
- Structural: 1:1:2 (4,000–5,000 PSI, use ready-mix)
Bags needed for small pours (using 80-lb bags): One 80-lb bag yields approximately 0.60 cu ft. So: Bags = Volume (cu ft) / 0.60
Example: 5 cu ft footing → 5 / 0.60 = 8.3 → buy 10 bags
Always add a 10% waste factor to any concrete order — over-estimating by a small amount is far less costly than running short mid-pour, which creates cold joints that weaken the structure.