Construction Material Calculators

Frequently Asked Questions

How many bags of concrete do I need for a 10×10 slab at 4 inches thick?

A 10×10 slab at 4 inches (0.333 ft) thick is 33.3 cubic feet, or about 1.23 cubic yards. You would need 74 bags of 60 lb concrete mix or 56 bags of 80 lb mix. At this volume, ready-mix delivery is worth getting quotes on.

How do I convert cubic feet to cubic yards?

Divide cubic feet by 27. There are 27 cubic feet in one cubic yard (3 ft × 3 ft × 3 ft = 27 ft³).

How much does a cubic yard of concrete weigh?

A cubic yard of concrete weighs approximately 3,900–4,050 pounds (about 2 tons) when wet.

When should I use ready-mix instead of bags?

Ready-mix concrete becomes more economical at volumes above 1 cubic yard (roughly 27 bags). For larger pours, always get ready-mix quotes.

Why should I add a waste buffer?

Adding 5–10% extra accounts for spillage, uneven subgrades, and forms that aren't perfectly square. It's much cheaper to have a little left over than to run short mid-pour.