Get the square footage right
Flooring, paint, sod, roofing quotes or a listing description: they all start with an accurate area. This calculator handles the most common shapes, rectangle, L-shape, circle and right triangle, and also gives the perimeter for baseboard, the flooring to buy with a waste allowance, and the cost.
Formulas by shape
| Shape | Area | Perimeter |
|---|---|---|
| Rectangle | length × width | 2 × (length + width) |
| L-shape | length × width + extension length × extension depth | 2 × (length + width + extension depth) |
| Circle | π × (diameter ÷ 2)² | π × diameter |
| Right triangle | base × height ÷ 2 | base + height + √(base² + height²) |
Use the same unit for every measurement. The calculator accepts feet, inches, yards and meters, and reports the area in square feet, square yards, square meters and acres.
Worked example: a 15 × 12 ft living room in vinyl plank
- Area: 15 × 12 = 180 sq ft.
- Perimeter: 2 × (15 + 12) = 54 ft of baseboard, before subtracting doorways.
- With 10% waste: 180 × 1.10 = 198 sq ft of flooring.
- At $3.50 per sq ft: 198 × 3.5 = $693.
If the room has an 8 × 6 ft alcove, the area becomes 180 + 48 = 228 sq ft and the perimeter 2 × (15 + 12 + 6) = 66 ft.
Cost by flooring type (198 sq ft to buy)
| Flooring (typical material price) | Price per sq ft | Material cost |
|---|---|---|
| Sheet vinyl or basic carpet | $1.50 | $297 |
| Laminate or vinyl plank | $3.50 | $693 |
| Mid-range porcelain tile | $5.00 | $990 |
| Engineered hardwood | $8.00 | $1,584 |
| Solid hardwood or natural stone | $12.00 | $2,376 |
These are material prices only. Professional installation typically adds $2 to $8 per sq ft depending on the material and subfloor preparation.
Measuring irregular rooms
Break the space into simple shapes, rectangles, triangles and half-circles, calculate each one and add them up. Subtract areas you will not cover, such as kitchen cabinets or a built-in island. Measure each wall at two heights because older rooms are rarely square, and use the larger value.
Feet and inches made easy
Convert inches to decimal feet before multiplying: divide the inches by 12. A wall of 12 ft 9 in is 12.75 ft. If you measured everything in inches, multiply length by width and divide by 144 to get square feet.
Measuring tips
A laser measure is faster and more accurate than a tape over long distances. Sketch the room and write each dimension on the drawing, then round up to the next inch. Order all the flooring at once so it comes from the same production lot, and keep a spare box for repairs.