How to calculate the cost of a concrete slab
- Multiply length × width in feet to get the area in square feet.
- Multiply by the thickness in inches ÷ 12 to get cubic feet.
- Divide by 27 for cubic yards and add 5 to 10 percent for uneven ground and spillage.
- Multiply cubic yards by your price per yard. Add delivery fees, reinforcement, forms and labor if a contractor is pouring it.
Worked example. A 12 × 12 ft patio, 4 inches thick: 144 ft² × 0.333 ft = 48 ft³. Add 5 percent: 50.4 ft³, or 1.87 yd³. At $180 per yard the concrete costs about $336, or 84 bags of 80 lb premix.
How much does a yard of concrete cost?
Concrete Network puts the US range at about $160 to $195 per cubic yard for ready-mix, with an average near $180. Prices vary by region, mix strength and distance from the plant, and small loads often carry an extra fee. Ask your local supplier and enter their price above.
How many bags of concrete do I need?
An 80 lb bag of Quikrete Concrete Mix yields about 0.60 ft³ and a 60 lb bag about 0.45 ft³. That works out to 45 bags of 80 lb or 60 bags of 60 lb per cubic yard.
| Slab, 4 in thick | Cubic yards | 80 lb bags | 60 lb bags |
|---|---|---|---|
| 4 × 4 ft pad | 0.20 | 9 | 12 |
| 10 × 10 ft | 1.23 | 56 | 75 |
| 12 × 12 ft | 1.78 | 80 | 107 |
| 20 × 20 ft | 4.94 | 223 | 297 |
Figures in the table add no extra for waste.
How thick should a concrete slab be?
| Use | Typical thickness |
|---|---|
| Driveway for cars and SUVs | 4 in minimum |
| Driveway for heavier vehicles | 5 in or more, with rebar |
Concrete Network notes that going from 4 to 5 inches can raise a driveway's load capacity by nearly 50 percent. Check local codes, which can set minimums for driveways and for slabs under buildings.
Questions about concrete slab costs
How much concrete do I need for a 10 × 10 slab?
At 4 inches thick, 33.3 ft³: about 1.23 cubic yards, or 56 bags of 80 lb premix, before extra for waste.
How many bags of concrete make a cubic yard?
About 45 bags of 80 lb mix or 60 bags of 60 lb mix, based on the yields printed on Quikrete Concrete Mix.
Is it cheaper to use bags or ready-mix?
Bags suit small pads and post holes. Once a job needs more than about a cubic yard, ready-mix is usually less work and often less money; enter both prices to compare. Many suppliers charge extra for small loads, so ask.
How thick should a concrete slab be?
Most residential driveways are at least 4 inches. Going to 5 inches adds load capacity for heavier vehicles, and thicker slabs usually need steel reinforcement.
Sources
- Bag yields, 0.45 ft³ (60 lb) and 0.60 ft³ (80 lb): Quikrete, Concrete Mix data sheet
- Ready-mix price, about $160 to $195 per cubic yard: Concrete Network, Concrete Prices
- Driveway thickness, 4 inches minimum, 5 inches for heavier loads: Concrete Network, How Thick Should a Concrete Driveway Be?
Last reviewed November 4, 2026. Found a wrong figure? Tell us.