Quick reference showing how much concrete you need for any area and thickness. Find your slab thickness, multiply by your square footage, and get cubic yards instantly.
| Thickness | CF/SF | CY / 100 SF | 80-lb Bags / 100 SF | 60-lb Bags / 100 SF |
|---|---|---|---|---|
| 2" | 0.167 | 0.62 | 28 | 37 |
| 3" | 0.250 | 0.93 | 42 | 56 |
| 4" | 0.333 | 1.24 | 56 | 75 |
| 5" | 0.417 | 1.54 | 70 | 93 |
| 6" | 0.500 | 1.85 | 84 | 112 |
| 8" | 0.667 | 2.47 | 112 | 149 |
| 10" | 0.833 | 3.09 | 139 | 186 |
| 12" | 1.000 | 3.70 | 167 | 223 |
4″ row highlighted — the most common residential slab thickness.
| Slab Size | Square Feet | Cubic Yards | 80-lb Bags |
|---|---|---|---|
| 4 × 4 ft | 16 | 0.20 | 9 |
| 6 × 6 ft | 36 | 0.44 | 20 |
| 8 × 10 ft | 80 | 0.99 | 45 |
| 10 × 10 ft | 100 | 1.23 | 56 |
| 10 × 12 ft | 120 | 1.48 | 67 |
| 12 × 12 ft | 144 | 1.78 | 80 |
| 12 × 20 ft | 240 | 2.96 | 134 |
| 20 × 20 ft | 400 | 4.94 | 222 |
| 20 × 24 ft | 480 | 5.93 | 267 |
| 24 × 24 ft | 576 | 7.11 | 320 |
Volume = Length (ft) × Width (ft) × Thickness (ft). Divide by 27 to get cubic yards. For thickness in inches, divide by 12 first.
Example: 10 × 10 ft slab at 4″ thick
10 × 10 × (4 ÷ 12) = 33.3 cu ft ÷ 27 = 1.23 cubic yards
Need a precise calculation with waste factor and cost? Use our Concrete Calculator.
Under 1 cubic yard (about 45 bags of 80-lb): bags are practical for small pours like footings, post holes, and small pads.
Over 1 yard: ready-mix delivery is almost always cheaper and saves hours of mixing labor. Most batch plants have a 1-yard minimum with delivery fees of $100–$200.
At the standard 4-inch thickness, a 10×10 slab needs 1.23 cubic yards — roughly 56 bags of 80-lb mix or 75 bags of 60-lb mix before waste factor.
4 inches for patios, walkways, and shed floors. 5–6 inches for driveways and garage floors that support vehicles. Footings are typically 8–12 inches deep depending on local code.
At 4 inches thick, one cubic yard covers about 81 square feet. At 6 inches thick, it covers about 54 square feet.
Yes. Add 10% for most pours to account for spillage, uneven ground, and form movement. Add 15% for irregular shapes or first-time pours.
Ready-mix typically costs $125–$175 per cubic yard depending on your region, mix design, and delivery distance. Short-load fees apply for orders under the truck minimum (usually 8–10 yards).
About 45 bags. Each 80-lb bag yields approximately 0.6 cubic feet, and there are 27 cubic feet in a cubic yard.