Concrete Slab Yardage Chart
Find your slab size in the left column and read across for the cubic yards of concrete at each thickness. All values are net volumes. A second table adds 10% waste and shows bag counts for a 4 in slab.
Net cubic yards by slab size and thickness
| Size (ft) | Area (ft²) | 3 in | 4 in | 5 in | 6 in |
|---|---|---|---|---|---|
| 10 × 10 | 100 | 0.93 | 1.23 | 1.54 | 1.85 |
| 12 × 12 | 144 | 1.33 | 1.78 | 2.22 | 2.67 |
| 12 × 16 | 192 | 1.78 | 2.37 | 2.96 | 3.56 |
| 12 × 20 | 240 | 2.22 | 2.96 | 3.70 | 4.44 |
| 16 × 16 | 256 | 2.37 | 3.16 | 3.95 | 4.74 |
| 20 × 20 | 400 | 3.70 | 4.94 | 6.17 | 7.41 |
| 20 × 24 | 480 | 4.44 | 5.93 | 7.41 | 8.89 |
| 24 × 24 | 576 | 5.33 | 7.11 | 8.89 | 10.67 |
| 24 × 30 | 720 | 6.67 | 8.89 | 11.11 | 13.33 |
| 30 × 30 | 900 | 8.33 | 11.11 | 13.89 | 16.67 |
| 30 × 40 | 1,200 | 11.11 | 14.81 | 18.52 | 22.22 |
| 40 × 40 | 1,600 | 14.81 | 19.75 | 24.69 | 29.63 |
The volume is length × width × thickness ÷ 12 ÷ 27. Values are rounded to two decimals for display; the calculators use unrounded numbers. For sizes not on the chart, use the slab calculator.
Order quantity with 10% waste, and bag counts at 4 in
| Size (ft) | Order (yd³) | Order (m³) | 80 lb bags | 60 lb bags |
|---|---|---|---|---|
| 10 × 10 | 1.36 | 1.04 | 62 | 82 |
| 12 × 12 | 1.96 | 1.50 | 88 | 118 |
| 12 × 16 | 2.61 | 1.99 | 118 | 157 |
| 12 × 20 | 3.26 | 2.49 | 147 | 196 |
| 16 × 16 | 3.48 | 2.66 | 157 | 209 |
| 20 × 20 | 5.43 | 4.15 | 245 | 326 |
| 20 × 24 | 6.52 | 4.98 | 294 | 392 |
| 24 × 24 | 7.82 | 5.98 | 352 | 470 |
| 24 × 30 | 9.78 | 7.48 | 440 | 587 |
| 30 × 30 | 12.22 | 9.34 | 550 | 734 |
| 30 × 40 | 16.30 | 12.46 | 734 | 978 |
| 40 × 40 | 21.73 | 16.61 | 978 | 1304 |
Above two cubic yards the bag counts become impractical for most people to mix by hand, which is why large slabs are normally ordered from a ready-mix plant. See bagged vs ready-mix.
Area covered by one cubic yard
| Thickness | Area covered (ft²) | Area covered (m²) |
|---|---|---|
| 3 in | 108.0 | 10.0 |
| 4 in | 81.0 | 7.5 |
| 5 in | 64.8 | 6.0 |
| 6 in | 54.0 | 5.0 |
| 8 in | 40.5 | 3.8 |
A quick way to check a quote: divide your area by the coverage figure. A 300 ft² patio at 4 in needs about 3.7 yd³ net.
How to use the chart
- Find the closest size row. If your slab lies between two rows, use the larger one or run the calculator.
- Choose the thickness column for your use. See the thickness guide.
- Add waste, usually 10%, and round up to the plant’s order step.
- For irregular shapes, add the volumes of rectangles.
- For footings, thickened edges and steps, add their volume separately.
Frequently asked questions
How many yards of concrete for a 20 × 20 slab?
4.94 yd³ net at 4 in, 5.43 yd³ with 10% waste.
How many yards for a 10 × 10 slab?
1.23 yd³ net at 4 in.
How many yards for a 12 × 12 slab?
1.78 yd³ net at 4 in.
Does the chart include waste?
The first table does not. The second adds 10%.
What thickness is the chart based on?
Four columns: 3, 4, 5 and 6 in.
How do I find sizes not shown?
Use the slab calculator.
Sources
Estimate only. Results depend on the numbers you enter, ground conditions and your supplier. For structural work consult a licensed engineer and follow local codes. Brand names such as Quikrete and Sakrete are used only to cite published product data. This site is not affiliated with any brand.