How Much Concrete for Common Slab Sizes
A slab 10 ft × 10 ft and 4 in thick takes 1.36 yd³ of concrete, or 62 × 80 lb bags of mix at the yield of 0.6 ft³[1], with the waste allowance of 10%[2] added. The table gives the same for other sizes and thicknesses.
Estimates for planning, not professional advice. Read the full notice.
Work it out for your own sizes
Enter your own slab sizeExample to try: Length 10 ft, Width 10 ft, Thickness 4 in
Concrete for common slab sizes
Cubic yards and 80 lb bags for common slab sizes at three thicknesses, with the waste allowance added
| Slab size (length × width) | Concrete at 4 in thick | 80 lb bags at 4 in thick | Concrete at 5 in thick | 80 lb bags at 5 in thick | Concrete at 6 in thick | 80 lb bags at 6 in thick |
|---|---|---|---|---|---|---|
| 4 ft × 4 ft | 0.22 yd³ | 10 × 80 lb bags | 0.27 yd³ | 13 × 80 lb bags | 0.33 yd³ | 15 × 80 lb bags |
| 8 ft × 8 ft | 0.87 yd³ | 40 × 80 lb bags | 1.09 yd³ | 49 × 80 lb bags | 1.3 yd³ | 59 × 80 lb bags |
| 10 ft × 10 ft | 1.36 yd³ | 62 × 80 lb bags | 1.7 yd³ | 77 × 80 lb bags | 2.04 yd³ | 92 × 80 lb bags |
| 10 ft × 12 ft | 1.63 yd³ | 74 × 80 lb bags | 2.04 yd³ | 92 × 80 lb bags | 2.44 yd³ | 110 × 80 lb bags |
| 12 ft × 12 ft | 1.96 yd³ | 88 × 80 lb bags | 2.44 yd³ | 110 × 80 lb bags | 2.93 yd³ | 132 × 80 lb bags |
| 12 ft × 16 ft | 2.61 yd³ | 118 × 80 lb bags | 3.26 yd³ | 147 × 80 lb bags | 3.91 yd³ | 176 × 80 lb bags |
| 12 ft × 20 ft | 3.26 yd³ | 147 × 80 lb bags | 4.07 yd³ | 184 × 80 lb bags | 4.89 yd³ | 220 × 80 lb bags |
| 16 ft × 16 ft | 3.48 yd³ | 157 × 80 lb bags | 4.35 yd³ | 196 × 80 lb bags | 5.21 yd³ | 235 × 80 lb bags |
| 20 ft × 20 ft | 5.43 yd³ | 245 × 80 lb bags | 6.79 yd³ | 306 × 80 lb bags | 8.15 yd³ | 367 × 80 lb bags |
| 24 ft × 24 ft | 7.82 yd³ | 352 × 80 lb bags | 9.78 yd³ | 440 × 80 lb bags | 11.73 yd³ | 528 × 80 lb bags |
| 20 ft × 30 ft | 8.15 yd³ | 367 × 80 lb bags | 10.19 yd³ | 459 × 80 lb bags | 12.22 yd³ | 550 × 80 lb bags |
| 30 ft × 40 ft | 16.3 yd³ | 734 × 80 lb bags | 20.37 yd³ | 917 × 80 lb bags | 24.44 yd³ | 1,100 × 80 lb bags |
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Each figure includes the waste allowance and is rounded up once. The bag counts use the yield of that bag size, from the maker's data sheet. Product names are trademarks of their owners. HoneyDoMath is not affiliated with, sponsored by or endorsed by these makers.
Bags or a truck load
A slab 10 ft × 10 ft and 4 in thick takes 62 × 80 lb bags, or 1.36 yd³ of concrete.
Truck mixers carry 8 yd³[2] to 12 yd³[2] per load. At a truck capacity of 8 yd³, a slab 24 ft × 24 ft at the same thickness takes 7.82 yd³ and fills 1 load, where bags would be 352 × 80 lb bags. A slab 20 ft × 30 ft takes 8.15 yd³ and needs 2 loads.
Questions
How much concrete do I need for a 10x10 slab?
The table lists that size at three thicknesses, in cubic yards and in bags, with the waste allowance added and the count rounded up once.
How many yards of concrete do I need for a 20x20 slab?
The table gives the cubic yards for that size at each thickness, so you can compare it with the truck capacity in the last section.
Do the figures include waste?
Yes. Each figure has the waste allowance added once, on the total, and the slab calculator lets you change the allowance.
Do I buy bags or order a truck?
That depends on the size of the pour and on what your supplier charges for each. The last section shows how many bags a job takes and when it fills a truck load; the price is your supplier's.
Calculate it for your project
Enter your own sizes to get the amount to buy or the layout figures, with the working shown and a page to print.
Check your slab in the slab calculatorSources (2)
-
QUIKRETE Concrete Mix No. 1101 data sheet (opens in new tab), The Quikrete Companies, Revised October 2022.
Manufacturer data.
“An 80 lb (36.2 kg) bag yields approximately 0.60 ft3 (17 L)”
Per QUIKRETE's data sheet, checked Nov 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 1) -
CIP 31, Ordering Ready Mixed Concrete (opens in new tab), National Ready Mixed Concrete Association, 2000, 2016, 2023.
Standards or industry body.
“Quantity of concrete ordered should be 4% to 10% more than an estimate calculated from the plan dimensions to account for contingencies.”
“The capacity of truck mixers varies between 8 to 12 cubic yards (5 to 9 m3).”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 2)
These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.