Calculate cubic yards, bags, and cost for any concrete slab — patios, driveways, garage floors, and foundations
Concrete slabs are the most common residential pour — patios, garage floors, driveways, shop floors, and foundations all use the same basic calculation. Here is a complete reference for 2026.
| Slab Dimensions | 4 inch | 5 inch | 6 inch |
|---|---|---|---|
| 8 x 8 ft | 0.79 yd3 | 0.99 yd3 | 1.19 yd3 |
| 10 x 10 ft | 1.23 yd3 | 1.54 yd3 | 1.85 yd3 |
| 10 x 20 ft | 2.47 yd3 | 3.09 yd3 | 3.70 yd3 |
| 12 x 12 ft | 1.78 yd3 | 2.22 yd3 | 2.67 yd3 |
| 16 x 20 ft | 3.95 yd3 | 4.94 yd3 | 5.93 yd3 |
| 20 x 20 ft | 4.94 yd3 | 6.17 yd3 | 7.41 yd3 |
| 24 x 24 ft | 7.11 yd3 | 8.89 yd3 | 10.67 yd3 |
A 10x10 slab at 4 inches thick needs approximately 1.23 cubic yards of concrete. Add 10% for waste and order 1.35 yards. At $150/yard that is about $203. In 80 lb bags you need 56 bags (62 with waste).
Residential patios and walkways need 4 inches. Driveways and garage floors should be 5-6 inches. Commercial or heavy-load slabs need 6-8 inches. Always check your local building code for minimum requirements before starting permitted work.
Materials only run $1.50-$3.50 per square foot. Fully installed with labor, forms, and finishing, expect $5-$10 per square foot. A 10x10 slab runs $500-$1,000 installed. A 20x20 slab runs $2,000-$4,000.
Concrete reaches 70% of its rated strength at 7 days and full design strength at 28 days. You can walk on it after 24-48 hours. Do not drive on a new residential slab for at least 7 days. Keep the surface moist for 7 days to ensure proper curing.