Square Footage Calculator
Measure each room or area in feet and inches. The calculator adds them up and converts the total, and can add flooring waste and a price per square foot.
How the square footage calculator works
Rectangle: square feet = length (ft) × width (ft). Convert inches first: 12 ft 6 in = 12.5 ft.
Circle: π × radius². Triangle: base × height ÷ 2. Split L-shaped rooms into rectangles and add them.
1 sq yd = 9 sq ft; 1 m² = 10.764 sq ft; 1 acre = 43,560 sq ft.
Flooring: add 5–10% for cuts and waste (10–15% for diagonal or patterned layouts).
Common room sizes
| Room | Area | Sq yd | m² |
|---|---|---|---|
| 10 × 10 ft | 100 sq ft | 11.1 | 9.29 |
| 10 × 12 ft | 120 sq ft | 13.3 | 11.15 |
| 12 × 12 ft | 144 sq ft | 16.0 | 13.38 |
| 12 × 15 ft | 180 sq ft | 20.0 | 16.72 |
| 15 × 20 ft | 300 sq ft | 33.3 | 27.87 |
| 20 × 20 ft | 400 sq ft | 44.4 | 37.16 |
| 24 × 24 ft | 576 sq ft | 64.0 | 53.51 |
| 30 × 40 ft | 1,200 sq ft | 133.3 | 111.48 |
Step-by-step guide
Related tools
Square Footage Calculator FAQ
How do I calculate square footage?
Multiply the length by the width in feet. A room 12 ft by 15 ft is 180 square feet. For odd shapes, split them into rectangles and add them.
How many square feet is 15 by 40?
15 × 40 = 600 square feet.
How much flooring do I need?
Take the room's square footage and add 5–10% for waste. A 180 sq ft room needs about 189–198 sq ft of flooring.