How Much Concrete for a Patio?
A typical patio is under one cubic yard — which puts you in the awkward zone between bags and a truck.
A 12×14 patio at 4 inches thick needs 0.76 cubic yards of concrete — 20.5 cubic feet, or 35 bags of 80 lb. That is below the one-yard minimum most ready-mix suppliers bill, so you would pay for a full yard either way.
Estimates only. Textured walls, high ceilings, sprayers and major colour changes can all increase the amount you need. Always buy slightly more than the calculation suggests.
Concrete needed by patio size
| Pour | Volume | Cubic yards | Bags | Cheaper |
|---|---|---|---|---|
| Small patio, 10 x 10 at 4" | 36.7 cu ft | 1.4 cu yd | 62 × 80 lb | Ready-mix |
| Standard patio, 12 x 14 at 4" | 61.6 cu ft | 2.3 cu yd | 103 × 80 lb | Ready-mix |
| Standard patio, 12 x 14 at 5" | 77 cu ft | 2.9 cu yd | 129 × 80 lb | Ready-mix |
| Large patio, 16 x 20 at 4" | 117.3 cu ft | 4.3 cu yd | 196 × 80 lb | Ready-mix |
| Large patio, 16 x 20 at 5" | 146.7 cu ft | 5.4 cu yd | 245 × 80 lb | Ready-mix |
| Very large patio, 20 x 30 at 4" | 220 cu ft | 8.1 cu yd | 367 × 80 lb | Ready-mix |
10 % waste, 80 lb bags. The 5-inch row reflects a patio that will take vehicle traffic or heavy furniture.
How thick should a patio slab be?
Four inches is the standard for a patio, walkway or shed base that only takes foot traffic and garden furniture.
Go to five or six inches if:
- A vehicle will ever drive onto it — even a ride-on mower or a car for a one-off delivery.
- You are placing heavy planters, a hot tub, or a masonry outdoor kitchen on it.
- The sub-base is soft or poorly compacted. Extra thickness partly compensates for a weak base, though fixing the base is the better answer.
Below the slab you need 4 inches of compacted gravel as a base. That is not optional: it drains water away and gives the slab something flat and stable to sit on. Concrete poured straight onto soil cracks.
The under-one-yard problem
A 12×14 patio needs 0.76 yards. You cannot buy 0.76 yards of ready-mix — the minimum is a yard, so you pay $165 and leave a quarter of it in the truck.
You have three options, and none is obviously right:
- Order the full yard anyway. You pay for concrete you do not use, but you get a fast, single, continuous pour with a good finish. For most people this is the right call.
- Use bags. 35 bags is $210 and about 2,800 lb of material. It is more expensive than the yard and much more work, and the finish will be harder to get flat because you are placing it in batches.
- Enlarge the pour. If you were considering a path, a pad for bins or a step, pouring it at the same time costs almost nothing — you are already paying for the yard.
Option three is the one people forget, and it is usually the best value.
Joints, and why a patio needs them
Concrete shrinks as it cures and moves with temperature. A patio poured as one unbroken slab will crack, and it will crack wherever it wants to.
Control joints give it a place to crack that you choose. The rule is a joint every 8 to 12 feet in both directions, cut to about a quarter of the slab depth. On a 12×14 patio that means at least one joint each way.
You also need:
- Expansion joints where the patio meets a wall, a step or another slab — a compressible strip, not a cut line.
- Reinforcement. Wire mesh or rebar does not stop cracking; it holds the slab together when it does crack. For a patio on a good base, mesh is cheap insurance.
- A slight slope. About 1 to 2 % away from the house, so water runs off rather than sitting against the wall.
Frequently asked questions
How much concrete for a 12x14 patio?
About 20.5 cubic feet with waste, which is 0.76 cubic yards or 35 bags of 80 lb mix, at 4 inches thick.
How thick should a concrete patio be?
Four inches for foot traffic and garden furniture. Five to six inches if a vehicle will drive on it or you are placing heavy planters or a hot tub.
Do I need gravel under a concrete patio?
Yes. Four inches of compacted gravel drains water away and gives the slab a flat, stable base. Concrete poured straight onto soil will crack.
Does a concrete patio need control joints?
Yes. Every 8 to 12 feet in both directions, cut to about a quarter of the slab depth. Without them the slab cracks wherever it chooses.