How to find square footage
Multiply length by width for each rectangle, in feet. For an L-shaped room, split it into two rectangles and add them. A triangle is half of length times width.
| To convert | Multiply by |
|---|---|
| Square feet → square yards | 0.1111 (÷ 9) |
| Square feet → square meters | 0.0929 |
| Square feet → acres | ÷ 43,560 |
How much concrete do I need?
Concrete is sold by the cubic yard. Multiply length × width × thickness (all in feet) to get cubic feet, then divide by 27. Add 5% to 10% for spills and uneven ground.
A 10 × 10 ft patio at 4 inches is about 1.23 cubic yards, or 1.36 with 10% extra. For premixed bags, an 80-lb bag makes about 0.6 cubic feet, a 60-lb bag about 0.45, and a 40-lb bag about 0.30. For more than about one cubic yard, ready-mix delivery is usually easier.
| Project | Typical thickness |
|---|---|
| Sidewalk, patio | 4 in |
| Driveway | 4 – 6 in |
| Garage floor, RV pad | 6 in |
Frequently asked questions
How much extra flooring should I buy?
About 10% for straight layouts, and 15% or more for diagonal or herringbone patterns, which create more cut pieces.
How many 80-lb bags are in a yard of concrete?
About 45 bags, since a cubic yard is 27 cubic feet and each 80-lb bag yields about 0.6 cubic feet.