How Much Concrete for a 15x20 Patio?
For a 15x20 patio poured 4 inches thick, plan on about 3.70 cubic yards of concrete. That comes from 300 square feet times 0.333 feet of depth, divided by 27. How much concrete for a 15x20 patio at other thicknesses is in the table below.
Concrete calculator →The math for a 15x20 patio
- Area: 15 ft × 20 ft = 300 sq ft.
- Thickness in feet: 4 in ÷ 12 = 0.333 ft.
- Volume: 300 × 0.333 = 100.0 cubic feet.
- Cubic yards: 100.0 ÷ 27 = 3.70 yd³.
- With 10% extra: 4.07 yd³.
The concrete calculator runs the same steps for any size and thickness.
Related: How Much Concrete for a 15x20 Slab?
Concrete for a 15x20 patio by thickness
| Thickness | Cubic feet | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags |
|---|---|---|---|---|---|
| 4 in | 100.0 | 3.70 | 4.07 | 167 | 223 |
| 5 in | 125.0 | 4.63 | 5.09 | 209 | 278 |
| 6 in | 150.0 | 5.56 | 6.11 | 250 | 334 |
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 Patio? Yards by Size
Placing the order
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.
Joints, mesh and rebar
Plan the joints before the pour. Panels close to square crack less than long, narrow ones, and joint spacing around 8 feet is typical for a 4-inch slab. Cut joints with a groover while the concrete is soft or with a saw within the first day.
Questions people ask
How many yards of concrete for a 15x20 patio at 4 inches?
About 3.70 cubic yards, or 4.07 with 10 percent extra.
How many yards for a 15x20 patio at 6 inches?
About 5.56 cubic yards.
How many 80 lb bags for a 15x20 patio?
About 167 bags at 4 inches thick, before any waste allowance.
How many square feet is a 15x20 patio?
300 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 24x24 Patio?
- How Much Concrete for a 15x15 Patio?
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