How Much Concrete for a 12x20 Patio?
For a 12x20 patio poured 4 inches thick, plan on about 2.96 cubic yards of concrete. That comes from 240 square feet times 0.333 feet of depth, divided by 27. How much concrete for a 12x20 patio at other thicknesses is in the table below.
Concrete calculator →The math for a 12x20 patio
- Area: 12 ft × 20 ft = 240 sq ft.
- Thickness in feet: 4 in ÷ 12 = 0.333 ft.
- Volume: 240 × 0.333 = 80.0 cubic feet.
- Cubic yards: 80.0 ÷ 27 = 2.96 yd³.
- With 10% extra: 3.26 yd³.
The concrete calculator runs the same steps for any size and thickness.
Related: How Much Concrete for a 12x20 Driveway?
Concrete for a 12x20 patio by thickness
| Thickness | Cubic feet | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags |
|---|---|---|---|---|---|
| 4 in | 80.0 | 2.96 | 3.26 | 134 | 178 |
| 5 in | 100.0 | 3.70 | 4.07 | 167 | 223 |
| 6 in | 120.0 | 4.44 | 4.89 | 200 | 267 |
Bag counts assume about 0.60 cubic feet per 80 lb bag and 0.45 per 60 lb bag, rounded up.
Choosing the thickness
Four inches is standard for a patio that sees foot traffic and furniture. Slope it about 1/8 to 1/4 inch per foot away from the house so rain runs off, and go thicker under a hot tub or outdoor kitchen.
Related: How Much Concrete for a 12x20 Slab?
Truck or bags?
A cubic yard of concrete is 27 cubic feet and weighs roughly 4,000 pounds. Most ready-mix trucks carry up to about 9 to 10 yards, though local trucks and rules vary. If your total is under a yard or two, bagged mix or a short-load supplier may be cheaper.
Prep before the pour
Uneven ground is the main reason pours run short. Every half inch of extra depth across the patio adds concrete you did not plan for. Screed the base flat, check it with a string line and set the forms to finished height before the truck arrives.
Keeping cracks under control
Cut or tool control joints so the slab cracks where you want it to. A common rule is spacing them, in feet, at no more than two to three times the slab thickness in inches, so about 12 feet apart for a 4-inch slab, and about a quarter of the slab depth deep.
Questions people ask
How many yards of concrete for a 12x20 patio at 4 inches?
About 2.96 cubic yards, or 3.26 with 10 percent extra.
How many yards for a 12x20 patio at 6 inches?
About 4.44 cubic yards.
How many 80 lb bags for a 12x20 patio?
About 134 bags at 4 inches thick, before any waste allowance.
How many square feet is a 12x20 patio?
240 square feet.
How much does a cubic yard of concrete weigh?
Roughly 4,000 pounds, or about 2 tons, for normal-weight concrete.
How thick should the base under the slab be?
About 4 inches of compacted gravel is common for residential slabs, more on soft or poorly drained soil.
Related guides
- How Much Area Does a Yard of Concrete Cover?
- How Many Bags of Concrete in a Yard? 40, 60, 80 lb
- Gravel Base Under a Concrete Slab: Depth and Tons
- How Many Yards in a Concrete Truck? Mixer Sizes
- Concrete Short Load Fee: What It Is and How to Cut It
- 60 lb vs 80 lb Concrete Bags: Yield, Count, and Cost
- Rebar vs Wire Mesh in a Slab: Which One to Use
- Cost to Pour a Concrete Slab: Per Square Foot
- How Much Concrete for a 12x16 Patio?
- How Much Concrete for a 12x18 Patio?
As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.