How this calculator works
Pick a shape and the calculator applies the matching area formula. For L-shaped rooms, split the space into rectangles, calculate each one and add them together.
Rectangle = Length × Width
Circle = π × (Diameter ÷ 2)²
Triangle = ½ × Base × Height
Trapezoid = (Side 1 + Side 2) ÷ 2 × Height
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Shape | Rectangle / square |
| Length | 12 ft |
| Width | 15 ft |
| Number of identical areas | 1 |
| Price per sq ft (optional) | $0 |
| Result | Value |
|---|---|
| Area | 180 sq ft |
| Square yards | 20 sq yd |
| Square meters | 16.72 m² |
| Acres | 0.0041 acres |
Step by step:
- Area = 12 × 15 = 180 sq ft
- × 1 = 180 sq ft
Common room sizes in square feet
| Room | Area | Square yards | Square meters |
|---|---|---|---|
| 10 × 10 ft bedroom | 100 sq ft | 11.11 sq yd | 9.29 m² |
| 12 × 12 ft | 144 sq ft | 16 sq yd | 13.38 m² |
| 12 × 15 ft | 180 sq ft | 20 sq yd | 16.72 m² |
| 14 × 16 ft living room | 224 sq ft | 24.89 sq yd | 20.81 m² |
| 20 × 20 ft two-car garage | 400 sq ft | 44.44 sq yd | 37.16 m² |
Common mistakes to avoid
- Measuring wall to wall in inches and forgetting to convert to feet.
- Adding L-shaped sections that overlap — split the shape so no part is counted twice.
Frequently asked questions
How do I measure an L-shaped room?
Divide it into two rectangles, find the area of each and add them.
How many square feet are in an acre?
43,560 square feet.