Area formulas
Rectangle = Length × Width
Triangle = Base × Height ÷ 2
Circle = 3.1416 × (Diameter ÷ 2)²
Converting feet and inches
Turn inches into decimal feet by dividing by 12: 6 in = 0.5 ft, 3 in = 0.25 ft, 9 in = 0.75 ft. So 12 ft 9 in is 12.75 ft.
Handy conversions
| From | To | Multiply by |
|---|---|---|
| Square feet | Square yards | ÷ 9 |
| Square feet | Square meters | × 0.0929 |
| Square feet | Acres | ÷ 43,560 |
| Square yards | Square feet | × 9 |
Measuring an L-shaped room
Draw the room and split it into two rectangles. Measure each, find their areas and add them. Measuring from the drawing avoids counting the overlap twice.
Frequently asked questions
How do I calculate square feet?
Multiply length by width in feet. A 12×10 ft room is 120 square feet.
How many square feet in an acre?
43,560 square feet — about the size of a 208×208 ft square.
How many square feet is a 10x10 room?
100 square feet.