Concrete Patio Calculator
Work out exactly how much concrete your patio slab needs — bags, cubic yards, ready-mix truckloads and cost.
Your patio
Split the patio into two rectangular sections.
4 in is standard for a patio; 5–6 in if it will carry vehicle weight.
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Slab breakdown
88 bags for 144 sq ft at 4 in thick
Mixing time
5 h 17 m
One person, 88 bags
Base & joint planner
The short answer
A 12×12 ft patio at the standard 4 inch thickness needs about 1.9 cubic yards of concrete, roughly 88 × 80 lb bags once waste is added. Work it out precisely by finding the area, multiplying by thickness in feet to get volume, adding 5–10% waste, then dividing by your bag’s yield — or converting to cubic yards for a ready-mix order on larger pours.
Concrete needed by patio size
Figures below assume a standard 4 inch thickness, no waste added.
| Patio size | Area | Volume | Cubic yards | 80 lb bags |
|---|---|---|---|---|
| 10×10 ft | 100 sq ft | 33.3 cu ft | 1.2 | 56 |
| 12×12 ft | 144 sq ft | 48 cu ft | 1.8 | 80 |
| 14×14 ft | 196 sq ft | 65.3 cu ft | 2.4 | 109 |
| 16×16 ft | 256 sq ft | 85.3 cu ft | 3.2 | 143 |
| 20×20 ft | 400 sq ft | 133.3 cu ft | 4.9 | 223 |
Past about 2 cubic yards, most people find ready-mix delivery more practical than hand-mixing dozens of bags.
How thick should a slab be?
| Use | Typical thickness |
|---|---|
| Stepping pad / small walkway | 3 in |
| Standard patio | 4 in |
| Patio with a hot tub or heavy furniture | 5 in |
| Driveway or area with vehicle weight | 5–6 in |
4 inches is the standard for a residential patio carrying foot traffic and typical outdoor furniture. Go thicker if the slab will support a hot tub, heavy planters, or any vehicle weight.
How to calculate concrete for a patio
A patio slab is a simple flat volume — area times thickness.
- Find the area. Length × width for a rectangle, π × radius² for a circle, or the sum of each section for an L-shape.
- Convert thickness to feet. Divide the thickness in inches by 12.
- Find the volume. Multiply area by thickness in feet to get cubic feet.
- Add waste. 5–10% covers spillage, subgrade unevenness and over-pour.
- Convert to bags or bulk. Divide cubic feet by your bag’s yield and round up, or divide cubic feet by 27 for cubic yards and order ready-mix.
Worked example
A 12×12 ft patio, 4 inches thick, using 80 lb bags:
- Area12 × 12 = 144 sq ft
- Thickness in feet4 ÷ 12 = 0.33 ft
- Volume144 × 0.33 = 48 cu ft
- Plus 10% waste52.8 cu ft
- Cubic yards52.8 ÷ 27 = 1.96
- Divide by bag yield52.8 ÷ 0.60 = 88
- Round up88 × 80 lb bags, or ~2 cu yd ready-mix
That’s over 7,000 lb of bagged concrete — a strong argument for ready-mix delivery on anything this size or larger.
Bagged concrete vs ready-mix
| Bagged concrete | Ready-mix delivery | |
|---|---|---|
| Best for | Small patios, repairs, under ~1–2 cu yd | Larger patios, driveways, anything over ~2 cu yd |
| Consistency | Depends on mixing technique | Uniform, batch-controlled |
| Labor | Heavy — mixing dozens of bags by hand or mixer | Low — truck pours directly |
| Cost per cubic yard | Usually higher | Usually lower at volume |
| Access needed | None — carry bags in | Truck access to the pour site |
Pouring a patio: a quick checklist
- Excavate and gradeRemove sod and soil to depth, sloping slightly away from the house for drainage.
- Compact a gravel baseAbout 4 inches of compacted gravel gives a stable, well-drained subgrade.
- Set formsStraight, level, well-staked forms keep the slab’s edges accurate.
- Add reinforcement if neededWire mesh, rebar, or fiber reinforcement helps control cracking, especially on larger slabs.
- Pour, screed and floatStrike off excess concrete level with the forms, then float the surface smooth.
- Cut control jointsJoints spaced by the slab’s thickness give cracks a place to happen on purpose.
- Cure properlyKeep the surface damp or covered for several days for full strength.
Common mistakes
- Pouring too thinA patio under 4 inches is more prone to cracking under furniture, planters or foot traffic over time.
- Skipping the gravel basePouring straight onto unprepared soil invites uneven settling and cracking.
- No control jointsWithout planned joints, concrete cracks wherever it wants — usually somewhere visible.
- Underestimating bag count for a big pourMixing 80+ bags by hand is a serious job — check the ready-mix comparison before committing to bags.
- Ignoring drainage slopeA flat or backward-sloping patio can pool water against the house foundation.
- Rushing the cureUsing the patio too soon, or letting it dry out too fast in hot weather, weakens the final surface.
What this calculator assumes
Adjust your result if your project differs from these.
- Bag yields of 0.60, 0.45, 0.375 and 0.30 cu ft for 80, 60, 50 and 40 lb bags
- The patio treated as a simple rectangle, circle, or two combined rectangles (L-shape)
- A uniform slab thickness across the whole area
- Standard concrete mix, not fiber, high-strength, or decorative/stamped mixes
- Ready-mix trucks holding about 10 cubic yards
- Mixing at about 6 minutes per 80 lb bag, per person
- Control joint spacing of about 2.5× the slab thickness (in feet) — a general rule of thumb, not an engineering design
- Prices are whatever you enter; they are not live market rates
Common questions
How much concrete do I need for a patio?
Multiply the patio’s area by its thickness in feet to get cubic feet, add 5 to 10 percent waste, then convert to bags or cubic yards. A 12×12 ft patio at 4 inches thick needs about 1.8 cubic yards, roughly 88 x 80 lb bags.
How thick should a concrete patio be?
4 inches is standard for a patio carrying foot traffic and furniture. Areas that will see vehicle weight need 5 to 6 inches or more.
Do I need rebar or mesh in a patio slab?
For a standard 4 inch patio on stable, well-compacted soil, many installers rely on fiber-reinforced concrete without steel mesh. Larger slabs, poor soil, or freeze-thaw climates benefit from wire mesh or rebar for crack control.
How much does a concrete patio cost per square foot?
Material cost alone for a basic broom-finished patio typically runs a few dollars per square foot; labor, finishing and forms add significantly more. Use your own local prices for an accurate total.
Should I use ready-mix or bagged concrete for a patio?
Past roughly 1 to 2 cubic yards, ready-mix delivery is usually more practical and often cheaper per cubic yard than bags, and ensures a consistent pour. Small patios or repairs are fine with bagged concrete.
How many bags of concrete for a 10×10 patio?
A 10×10 ft patio at 4 inches thick needs about 33 cubic feet of concrete before waste, roughly 61 x 80 lb bags including a 10 percent waste allowance.
How deep should the gravel base be under a patio?
A compacted gravel base of about 4 inches is typical under a residential patio, improving drainage and providing a stable, even subgrade.
How far apart should control joints be in a patio?
A common rule of thumb is spacing in feet equal to about 2 to 3 times the slab thickness in inches, so a 4 inch thick patio typically gets joints every 8 to 12 feet.
How long does a concrete patio need to cure before use?
Light foot traffic is usually fine after about 24 to 48 hours. Furniture and regular use should wait about 7 days, with full strength reached around 28 days.
Can I pour a patio over an existing surface?
Pouring over an existing slab is sometimes possible if it’s structurally sound, but it adds height and needs a bonding agent or thickened overlay. Removing the old surface and starting from a prepared subgrade is more reliable.
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Concrete Patio Estimate
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materialcalculate.com/tools/concrete-patio-calculator/
Project
| Patio shape | — |
| Dimensions | — |
| Thickness | — |
| Waste allowance | — |
Volume
| Concrete volume | — |
| Weight | — |
| Ready-mix trucks (~10 cu yd each) | — |
Total shopping list
| 80 lb bags | — |
| 60 lb bags | — |
| 40 lb bags | — |
| Estimated cost | — |
Notes
Estimate generated by materialcalculate.com. Assumes a uniform-thickness slab and standard concrete mix with yields of 0.60, 0.45, 0.375 and 0.30 cu ft for 80, 60, 50 and 40 lb bags. Confirm quantities with your supplier before buying.