How much concrete,
in cubic yards.
Enter the dimensions of your slab, patio, or footing. Get the concrete volume in cubic yards, cubic feet, and bags — with an automatic 10% overage allowance for spillage and uneven subgrade.
Overage is a flat 10% on top of the measured volume, then bags are rounded up to whole bags. Yields are the manufacturer figures for standard concrete mix (Quikrete Concrete Mix No. 1101); high-strength, fast-setting and crack-resistant mixes yield the same per bag, but check the bag if you are using a specialty product.
When to call a truck.
Bagged concrete is fine for fence posts, small repairs, and projects under about half a yard. Beyond that, the labor and number of bags adds up fast:
- Under 0.3 yd³ (~8 ft³): bagged is most economical.
- 0.3 – 1.0 yd³: bagged works but you're mixing 25–60 bags.
- Over 1 yd³: ready-mix delivery wins on labor and consistency.
- Over 3 yd³: definitely ready-mix; most plants have a 1 yd³ minimum.
Ready-mix is usually priced per cubic yard with a delivery fee and short-load surcharge for orders under 5 yd³.
| 1 cubic yard | 27 ft³ |
| 80 lb bags | 45 bags |
| 60 lb bags | 60 bags |
| 40 lb bags | 90 bags |
Always add 5–10% extra. Concrete waste from uneven ground is common.
Concrete needed by project.
| Project | Dimensions | Concrete needed |
|---|---|---|
| Sidewalk section | 3 × 3 × 4 in | 3 ft³ · 0.11 yd³ |
| Fence post hole | 10 × 10 × 36 in | 2 ft³ · 0.07 yd³ |
| Shed pad | 8 × 8 × 4 in | 21 ft³ · 0.79 yd³ |
| Patio | 10 × 12 × 4 in | 40 ft³ · 1.48 yd³ |
| Single garage floor | 12 × 20 × 4 in | 80 ft³ · 2.96 yd³ |
| Driveway (small) | 20 × 12 × 4 in | 80 ft³ · 2.96 yd³ |
| Driveway (large) | 40 × 12 × 4 in | 160 ft³ · 5.93 yd³ |