Concrete Calculator
Estimate cubic yards of concrete and number of bags for any slab, footing, or column.
About the Concrete Calculator
Whether you're pouring a driveway, sidewalk, patio, or footing, accurate concrete volume calculation prevents costly under-ordering or excessive waste. Concrete is sold by the cubic yard for ready-mix trucks, and by the 60 lb or 80 lb bag for small projects.
The Formula
Volume (cubic yards) = (Length × Width × Thickness in feet) ÷ 27. Since 1 cubic yard = 27 cubic feet, divide by 27 to convert. Always add 10% for waste and settling.
Bags vs. Ready-Mix
An 80 lb bag of standard concrete mix yields approximately 0.60 cubic feet. A 60 lb bag yields about 0.45 cubic feet. A 40 lb bag yields about 0.30 cubic feet. For projects requiring more than 1 cubic yard (27 bags of 80 lb mix), ready-mix delivery is usually more cost-effective and easier to work with.
Recommended Slab Thickness
Standard sidewalk: 4 inches | Driveway (passenger cars): 4–6 inches | Driveway (heavy trucks/RVs): 6 inches | Patio: 4 inches | Garage floor: 4–6 inches | Structural footings: 8–12 inches (consult local building codes)
Concrete Mix Strength
Concrete strength is measured in PSI (pounds per square inch). Standard mix (2,500–3,000 PSI) suits most residential slabs. High-strength mix (4,000–5,000 PSI) is used for driveways and footings exposed to heavy loads. Fiber-reinforced concrete reduces cracking.
Ordering Tips
Ready-mix trucks typically carry 8–10 yards. Most suppliers have a minimum order (often 1 yard) with short-load fees for less. Order early in the morning so the concrete doesn't set during transport in hot weather. Have your forms, tools, and crew ready before the truck arrives.