Concrete Patio Calculator
A concrete patio calculator finds cubic yards as length × width × depth (ft) ÷ 27: a 12 × 12 ft patio 4 in thick needs 1.78 yd³, or 1.96 yd³ with 10% extra.
How much concrete do I need for a patio?
A concrete patio calculator multiplies length by width by thickness in feet and divides by 27 to get cubic yards, the unit ready-mix plants sell. Thickness is entered in inches and divided by 12 for you. A 12 × 12 ft patio at the standard 4 inches holds 1.78 cubic yards. Tick the 10% waste box and the order becomes 1.96 cubic yards.
Enter the patio’s length and width in feet, the slab depth in inches, and your price per cubic yard. The cost line multiplies the yards by that price, so it covers concrete only, not delivery fees, reinforcement, or labor.
The formula in plain words
- Cubic feet = length × width × (depth in inches ÷ 12)
- Cubic yards = cubic feet ÷ 27
- With waste = cubic yards × 1.10
- Cost = cubic yards × price per yard
Concrete is ordered to the quarter yard at most plants. Round your result up to the next quarter before you call.
Worked examples
Both use $150 per cubic yard.
- Square patio, 12 × 12 ft, 4 in**
- Cubic feet: 12 × 12 × 0.333 = 48 cu ft
- Cubic yards: 48 ÷ 27 = 1.78 yd³ ($266.67)
- With 10% waste: 1.96 yd³ ($293.33)
- Order: 2 cubic yards
- Family patio, 16 × 20 ft, 4 in**
- Cubic feet: 16 × 20 × 0.333 = 106.7 cu ft
- Cubic yards: 106.7 ÷ 27 = 3.95 yd³ ($592.59)
- With 10% waste: 4.35 yd³ ($651.85)
- Order: 4.5 cubic yards
Pour the same 16 × 20 patio at 5 inches and it jumps to 4.94 yd³ before waste. One inch of depth adds a full cubic yard here.
Concrete for common patio sizes at 4 inches
| Patio size | Cubic yards | With 10% | 80-lb bags (no waste) |
|---|---|---|---|
| 10 × 10 ft | 1.23 | 1.36 | 56 |
| 10 × 12 ft | 1.48 | 1.63 | 67 |
| 12 × 12 ft | 1.78 | 1.96 | 80 |
| 12 × 16 ft | 2.37 | 2.61 | 107 |
| 16 × 20 ft | 3.95 | 4.35 | 178 |
| 20 × 20 ft | 4.94 | 5.43 | 223 |
| 24 × 24 ft | 7.11 | 7.82 | 320 |
Bags assume 0.6 cubic feet per 80-lb bag. Past about 80 bags, mixing by hand becomes a long, hard day, and cold joints between batches become likely.
Ready-mix truck or bags?
For the 12 × 12 ft patio, 1.96 cubic yards is about 88 bags of 80-lb mix once waste is included. That is roughly 7,000 lb of bags to lift, haul, and mix in a few hours before the first batches start to set. A ready-mix truck delivers the same volume in one pour, so the whole slab cures evenly. Many plants charge a short-load fee on small orders, so ask for the delivered price of your exact yardage and compare it with the bag total before you decide.
How to measure and prepare
- Measure the finished slab, not the dug-out area. Forms set the final size.
- Measure depth inside the forms at several points. Uneven ground often makes some spots deeper than planned.
- Plan slope. Patios are commonly sloped about 1/8 to 1/4 inch per foot away from the house so water drains off.
- Lay a base. Most patios sit on 4 inches or so of compacted gravel. Size it with the gravel base calculator.
- For curved edges, measure the largest enclosing rectangle, or split the shape into a rectangle plus a half circle.
Common mistakes
- Ordering the exact volume. Low spots in the base swallow extra concrete. A truck coming back for a quarter yard costs far more than ordering a bit over.
- Forgetting thickened edges. Some patios have a deeper edge along the perimeter. Add it as a separate strip.
- Pouring straight onto soft soil. Soft spots settle and crack the slab above them.
- Skipping joints. Concrete shrinks as it cures. Without control joints, it picks its own crack lines.
Related calculators
To price the whole project with labor, use the concrete patio cost calculator. For a decorative finish, see the stamped concrete cost calculator. Small patios mixed by hand can be counted in bags with the concrete bag calculator.
Frequently asked questions
What depth should a concrete patio be?
4 inches is the usual thickness for a patio that carries people, furniture, and grills, and it is this calculator's default. If a car or a hot tub will sit on part of it, thicken that area to 5 or 6 inches. Going from 4 to 5 inches adds 25% more concrete across the whole slab.
How many bags of concrete for a 10 × 10 patio?
A 10 × 10 ft patio at 4 inches is 33.3 cubic feet, or 1.23 cubic yards. At 0.6 cubic feet per 80-lb bag that is 55.6, so 56 bags before waste, and about 62 with 10% extra. Above roughly 1 cubic yard, ready-mix delivery is usually less work and often similar in cost.
Does a patio need rebar or wire mesh?
Many patios use welded wire mesh or #3 or #4 rebar for crack control, especially on larger slabs or soft, expansive soils. Reinforcement holds cracks tight; it does not stop them forming. This calculator covers concrete only, so price reinforcement separately.
Broom finish or stamped concrete — does it change how much concrete I need?
No. Volume depends only on the footprint and the thickness. A stamped finish adds labor, color, and sealer, which shows up on the stamped concrete cost calculator, not in the cubic yards.
How do I plan control joints on a patio?
A common rule of thumb spaces joints at 2 to 3 times the slab thickness in inches, read as feet. A 4-inch patio gets joints every 8 to 12 ft, cut about one quarter of the slab depth (1 inch). Keep the panels close to square. Joints do not change the volume you order.
Estimates only. Verify quantities with your supplier before purchasing.