Concrete Patio Calculator
A 16×12 ft patio at 4 inches thick needs about 2.4 cubic yards of concrete — roughly 107 bags of 80-lb mix with waste. Enter your dimensions below for the exact volume, bag count, and cost estimate.
Pro Tips
- →Patios typically need 4 inches of concrete thickness
- →Add a 2% slope away from your house for drainage
- →Consider decorative finishes like stamping or staining
- →Include 10% extra concrete for waste
- →Compact the gravel base thoroughly before pouring
Includes 10% waste factor
That's typically a professional pour. See costs ↓
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Cost Estimate
Estimated material costs for your project
Recommendation: Ready-Mix Concrete
For projects over 1 cubic yard, ready-mix is typically more economical and easier to work with.
118 bags × 80lb
2.61 cubic yards + delivery
192 sq ft × $3.00–$8.00/sq ft
Prices vary by location and time. Contact local suppliers for accurate quotes.
For general step-by-step instructions, read our complete Patio Thickness and Patio Guide.
How to Calculate Patio Concrete Volume
Concrete volume is a simple three-dimensional calculation: length × width × thickness. The only catch is that patio thickness is given in inches while length and width are in feet, so you convert thickness to feet first (divide inches by 12), then divide the cubic-foot result by 27 to get cubic yards — the unit ready-mix is sold in.
The full formula:
Cubic yards = (Length ft × Width ft × Thickness ft) ÷ 27
Worked example for a 16×12 ft patio at 4 inches (0.333 ft):
- 16 × 12 × 0.333 = 64 cubic feet
- 64 ÷ 27 = 2.37 cubic yards (before waste)
The 27 comes from one cubic yard being 3 ft × 3 ft × 3 ft. The how to calculate concrete guide covers the math for every shape; the calculator at the top of this page does the conversion automatically.
Patio Concrete Volume by Common Size
The table below gives cubic yards at the standard 4-inch patio thickness for the sizes homeowners build most often. These figures are raw volume — add waste separately (covered below).
| Patio Size | Square Feet | Cubic Feet (4 in) | Cubic Yards (4 in) |
|---|---|---|---|
| 10×10 ft | 100 | 33.3 | 1.23 cu yd |
| 12×12 ft | 144 | 48.0 | 1.78 cu yd |
| 14×16 ft | 224 | 74.7 | 2.76 cu yd |
| 16×18 ft | 288 | 96.0 | 3.56 cu yd |
| 20×20 ft | 400 | 133.3 | 4.94 cu yd |
Volume scales linearly with area, so a patio twice the square footage needs twice the concrete at the same thickness. To estimate any size not listed, multiply square feet by 0.0123 to get cubic yards at 4 inches.
Bag Counts for Small Patios
Bagged concrete makes sense only for small patios. An 80-lb bag of pre-mixed concrete yields about 0.60 cubic feet of finished concrete; a 60-lb bag yields about 0.45 cubic feet. Divide your cubic-foot volume by the bag yield to get the count, then add waste.
| Patio Size | Cubic Feet (4 in, +10%) | 80-lb Bags | 60-lb Bags |
|---|---|---|---|
| 8×8 ft | 23.5 | 40 bags | 53 bags |
| 10×10 ft | 36.7 | 62 bags | 82 bags |
| 12×12 ft | 52.8 | 88 bags | 118 bags |
At roughly 60 bags and up you are mixing, lifting, and emptying a pallet of material by hand — most people switch to ready-mix before that point. Our how many bags of concrete guide covers yields for every bag size, and the ready-mix vs bagged guide helps you decide.
Always Add 10% for Waste
Never order the exact calculated volume. Spillage, uneven subgrade, over-excavated low spots, and form spread all consume extra concrete. Industry practice is to add 10% for a flat patio on prepared ground; bump to 15% if the subgrade is rough or hand-graded.
| Base Volume (cu yd) | +10% Waste | +15% Waste |
|---|---|---|
| 1.23 (10×10) | 1.35 | 1.41 |
| 1.78 (12×12) | 1.96 | 2.05 |
| 2.76 (14×16) | 3.04 | 3.17 |
| 3.56 (16×18) | 3.92 | 4.09 |
| 4.94 (20×20) | 5.43 | 5.68 |
Running short mid-pour means a cold joint or an emergency second delivery, both far costlier than the 10% buffer.
Ready-Mix vs. Bagged Crossover
The practical crossover point for patios is around 1 to 2 cubic yards. Below it, bagged mix is convenient and avoids delivery minimums; above it, the labor of hand-mixing dozens of bags outweighs any savings, and ready-mix delivered by truck is faster and more consistent.
| Volume | Bags (80-lb) | Recommendation |
|---|---|---|
| Under 1 cu yd | Under ~45 | Bagged — mix as you go |
| 1–2 cu yd | ~45–90 | Either; ready-mix if a truck minimum fits |
| Over 2 cu yd | Over ~90 | Ready-mix delivery |
Ready-mix trucks typically have a load minimum (often 1 cubic yard) and may charge a short-load fee below a full truck (about 10 cu yd per the NRMCA standard truck capacity). For most 12×12 ft and larger patios, ready-mix wins on both effort and finish quality.
Patio Thickness and the IRC Standard
Use 4 inches for any standard patio. Four inches handles foot traffic, outdoor furniture, planters, and grills with margin to spare, and it is the minimum specified for residential slabs in the IRC — Section R506.2.3 calls for a minimum 3.5-inch slab thickness, with 4 inches being the standard build figure once a vapor retarder and tolerance are accounted for. Thickness drives volume directly: going from 4 to 5 inches adds 25% more concrete.
| Thickness | Cubic Yards per 100 sq ft | When to Use |
|---|---|---|
| 4 in | 1.23 cu yd | Standard patios — foot traffic, furniture, grills |
| 5 in | 1.54 cu yd | Heavy hot tubs, occasional light vehicle |
| 6 in | 1.85 cu yd | Vehicle loads or freeze-thaw-prone subgrade |
For most homeowners, paying for a 6-inch patio is over-building. See the patio thickness guide for the full breakdown of when extra depth is worth it.
Measuring L-Shaped, Curved, and Round Patios
Most patios are not perfect rectangles. The reliable method is to break any complex shape into simple pieces, calculate each piece's volume, and add them up.
- L-shaped or T-shaped: Split the footprint into two or three rectangles. Calculate cubic yards for each (length × width × 0.333 ÷ 27 at 4 in), then sum.
- Round patio: Use the area of a circle, π × r², where r is the radius in feet. A 12-ft-diameter round patio has r = 6, so area = 3.1416 × 36 = 113 sq ft; at 4 inches that is 113 × 0.333 ÷ 27 = 1.39 cu yd.
- Curved edge: Approximate the curve as a rectangle plus a half-circle (or quarter-circle), then add the pieces.
| Shape | Area Formula | Example (4 in) |
|---|---|---|
| Rectangle | L × W | 14×16 = 224 sq ft → 2.76 cu yd |
| L-shape | sum of rectangles | 12×12 + 6×8 = 192 sq ft → 2.37 cu yd |
| Round (12 ft dia) | π × r² | 113 sq ft → 1.39 cu yd |
Measure to the inside face of your forms and re-measure the actual dug area before ordering.
Base, Subgrade, and Next Steps
Concrete volume assumes a prepared base. A patio needs 4–6 inches of compacted gravel under the slab for drainage and to prevent settling; this base does not change concrete volume, but soft low spots in an over-dug subgrade silently absorb extra cubic yards. Compact and screed the base flat before ordering. See the gravel under concrete guide for base depth.
Once your volume is dialed in, get a price: the concrete patio cost calculator adds labor and finishes for a full installed estimate, and the concrete cost calculator breaks down per-square-foot pricing by region. Use the calculator above to lock in your exact cubic yards and bag count.