Slab
Footing
Column
Stairs
Bags
Material & Cost Options
Why Accurate Concrete Calculation Matters
Concrete is heavy, expensive, and time-sensitive. Running out mid-pour is a disaster. Over-ordering wastes money. Our concrete calculator gives you exact cubic yards and bag counts for slabs, footings, columns, and stairs — with a smart waste factor to cover uneven ground and spillage.
Whether you're searching "how many bags of concrete for a 10x10 slab" or "cubic yards calculator for footing", this tool provides professional accuracy that saves you from costly mistakes.
- Slab volume: Length × Width × (Thickness/12) in cubic feet.
- Footing volume: Length × (Width/12) × (Depth/12).
- Column volume: π × (Diameter/24)² × Height/12.
- Stairs volume: (Run × Rise × Width × Steps)/1728 + Platform volume.
All calculations run in your browser. No data is stored.
Bag Count vs. Ready-Mix
- 80 lb bag: yields 0.6 cubic feet. (Approx 45 bags per cubic yard)
- 60 lb bag: yields 0.45 cubic feet. (Approx 60 bags per cubic yard)
- 40 lb bag: yields 0.30 cubic feet. (Approx 90 bags per cubic yard)
- Ready-mix truck: Typically delivered in cubic yards (1 yard = 27 cu ft). Minimum order may apply.
For projects larger than 1 cubic yard, ready-mix is usually cheaper and less labor-intensive.
Concrete FAQ
Multiply length × width in feet, then divide by 80 (for 80 lb bags) to get approximate bags. For 10x10 slab: 100 ÷ 80 = 1.25, so about 21 bags (with 10% waste). Use calculator for exact.
Under 1 cubic yard, bags are convenient. Over 1 yard, ready-mix is typically 30-50% cheaper and ensures consistent quality. Our cost comparison helps you decide.
Footings must extend below the frost line (12-48" depending on climate). Width is typically 12-24". Consult local building codes.
No. Bag yields assume proper mixing with the recommended water amount. Excess water weakens concrete but doesn't significantly change volume.