🧱 Concrete Calculator
Concrete Coverage Guide
| Bag Size | Yield (cu ft) |
|---|---|
| 40-lb bag | 0.30 cu ft |
| 60-lb bag | 0.45 cu ft |
| 80-lb bag | 0.60 cu ft |
| 1 cu yard | 27 cu ft |
⚠️ Always order 5–10% extra to account for waste and spillage.
Frequently Asked Questions
Volume (cubic yards) = Length(ft) × Width(ft) × Thickness(ft) ÷ 27. Add 10% for waste and spillage. Example: a 10×10 ft slab at 4 inches thick = 10 × 10 × 0.333 ÷ 27 = 1.23 cubic yards. Order at least 1.36 cubic yards (10% extra).
An 80 lb bag yields approximately 0.60 cubic feet. A 60 lb bag yields 0.45 cubic feet. Divide your total cubic feet by the yield per bag. For the 10×10 slab example (33.3 cubic feet): 33.3 ÷ 0.60 = 56 bags of 80 lb concrete.
Residential driveways: 4 inches. Sidewalks and patios: 4 inches. Garage floors: 4–6 inches. Structural slabs: 4–8+ inches depending on load. Always check local building codes for your specific application.
For large projects (more than 1 cubic yard), ready-mix delivered by truck is more economical and ensures consistent quality. For small projects (under 0.5 cubic yards), bagged concrete is more practical. The break-even point is roughly 25–30 bags.