GUIDE深度 · Deep dive
How Much Concrete Do I Need?
Concrete volume is area times thickness, converted to cubic yards. Real ordering also needs 5 to 10 percent waste and a check on the ready-mix minimum.
The volume formula
Length times width times thickness in feet, divided by 27, gives cubic yards. If thickness is in inches, divide it by 12 first.
Bags or ready-mix
A 60-pound bag yields about 0.45 cubic feet and an 80-pound bag about 0.60. Above one cubic yard, ready-mix is usually less labor.
Waste and subbase
Add 5 to 10 percent waste. Gravel subbase and compaction are separate; do not mix them into the concrete volume.
FAQ
How much concrete is one square foot at 4 inches?
At 4 inches, one square foot is about 0.0123 cubic yards; a 10 by 10 slab is about 1.23 cubic yards.
How much waste should I add?
Add 5 percent for a flat slab and 10 percent for irregular ground or a first pour.