Concrete Patio Calculator
Enter your patio size and thickness to get cubic yards, bags and cost. Use the L-shape or round option for patios that are not a simple rectangle.
Last updated November 13, 2026
How much concrete for a patio?
Patio volume = length × width × thickness. At the usual 4 inches, divide the square footage by 81 to get cubic yards.
Example: a 12 ft × 16 ft patio is 192 square feet. 192 ÷ 81 = 2.37 cubic yards. With 10% for waste, order 2.75 yards.
Concrete for common patio sizes
All rows are 4 inches thick. The last two columns include 10% for waste.
| Patio size (ft) | Square feet | Cubic yards | Cubic yards + 10% | 80 lb bags + 10% |
|---|---|---|---|---|
| 10 × 10 | 100 | 1.23 | 1.36 | 62 |
| 10 × 12 | 120 | 1.48 | 1.63 | 74 |
| 12 × 12 | 144 | 1.78 | 1.96 | 88 |
| 12 × 16 | 192 | 2.37 | 2.61 | 118 |
| 14 × 14 | 196 | 2.42 | 2.66 | 120 |
| 16 × 16 | 256 | 3.16 | 3.48 | 157 |
| 16 × 20 | 320 | 3.95 | 4.35 | 196 |
| 20 × 20 | 400 | 4.94 | 5.43 | 245 |
Patios that are not rectangles
- L-shaped: pick the L-shape option and enter the overall size and the missing corner.
- Round: pick Round slab and enter the diameter.
- Curved or freeform: break it into rectangles and circles, add each as an area, and use 10% to 15% waste.
Bags or a truck?
Most patios are over 1 cubic yard, which is 45 bags of 80 lb mix. That is usually the point where ready-mix is easier. Enter your local prices above to compare, or read bagged concrete vs ready-mix.
Frequently asked questions
How much concrete do I need for a 12×12 patio?
A 12 ft × 12 ft patio at 4 inches thick is 1.78 cubic yards. With 10% for waste, order 2 yards or buy 88 bags of 80 lb mix.
How thick should a concrete patio be?
Four inches is the usual thickness for a patio that carries foot traffic and furniture. Go thicker for a hot tub or a vehicle, and check your local code.
How much concrete for a 16×20 patio?
A 16 ft × 20 ft patio at 4 inches thick is 3.95 cubic yards, or 4.35 yards with 10% for waste.
Do I need gravel under a patio?
A compacted gravel base is common practice because it drains and gives even support. The depth depends on your soil and climate.