Estimate cubic yards, bag count, and ready-mix cost for slabs, footings, sonotubes, and more.
Cubic yards, bags & cost
Results are planning estimates. Confirm quantities with your concrete supplier before ordering.
Concrete is measured by volume. For slabs and footings, multiply length × width × depth to get cubic feet, then divide by 27 for cubic yards. Sonotubes use a cylinder formula.
One 80 lb bag yields about 0.60 cubic feet. One cubic yard = 27 cubic feet. So you need approximately 45 bags of 80 lb to make one cubic yard of concrete.
| Project Size | Best Option | Why |
|---|---|---|
| Under 1 yard | Bagged | No truck minimum |
| 1–3 yards | Either | Compare total cost |
| Over 3 yards | Ready-mix | Faster, cheaper per yard |
A 10 ft × 10 ft slab at 4 inches thick needs about 1.24 cubic yards (33.3 cubic feet). At 6 inches thick, it needs approximately 1.85 cubic yards. Always add 5–10% waste.
A short-load fee is charged when you order less than the minimum load a ready-mix truck carries (usually 7–10 yards). This fee can significantly increase cost per yard on small orders, making bagged concrete more practical for small pours.
Residential driveways typically use 3,000–4,000 PSI concrete. In cold climates with freeze-thaw cycles, 4,000 PSI or higher is recommended. Ask your local ready-mix supplier what is standard for your region.
Double-check your depth input — it must be in inches, not feet. Also verify that length and width are in feet. Adding a 5–10% waste factor brings estimates closer to real-world requirements.
Concrete reaches about 70% strength in 7 days and full design strength in 28 days. Light foot traffic is usually safe after 24–48 hours. Avoid vehicle traffic for at least 7 days on a standard residential pour.