Unit system
Length
Width
Depth/Thickness
Result (click to copy)
Frequently Asked Questions
How much concrete do I need?
Multiply length × width × depth to get volume. For a 10ft × 12ft × 4in slab: 10 × 12 × (4/12) = 40 cubic feet = 1.48 cubic yards. Always add 10% for waste and spillage.
How many bags of concrete per cubic yard?
A 60lb bag makes about 0.45 cubic feet (0.017 cubic yards). A 80lb bag makes about 0.60 cubic feet (0.022 cubic yards). You need about 45 × 60lb bags or 34 × 80lb bags per cubic yard.
When should I use ready-mix vs bags?
For small projects under 1 cubic yard, bags are cheaper and more practical. For larger projects (driveways, foundations), ready-mix concrete delivered by truck is more cost-effective and ensures consistent mixing quality.