Square footage is the size of a flat surface measured in square feet — the number you need before you order flooring, paint a ceiling, seed a lawn or compare apartments. The calculator above handles rectangles, circles and triangles in feet, inches, yards or meters, adds a waste allowance, and turns the result into a cost estimate if you know the price per square foot.
How to use the square footage calculator
- Pick the shape. Most rooms are rectangles. Use circle for round patios or rugs and triangle for gables or corner beds.
- Enter the measurements. Choose the unit next to each box. If you measured 10 ft 6 in, either type 10.5 ft or switch to inches and type 126.
- Set how many identical areas. Three bedrooms of the same size? Enter 3 instead of running the calculator three times.
- Add waste if you are buying material. Flooring, tile and sod lose pieces to cuts. 5–10% is common; see the table below.
- Optionally enter a price. With a price per square foot, the calculator multiplies it by the area you need to buy.
The result updates as you type. Use the menu beside each result to switch between square feet, square yards, square meters, square inches or acres.
Square footage formulas
Every shape reduces to a short formula. All measurements must be in the same unit before you multiply.
Circle: A = π × r² (r = diameter ÷ 2)
Triangle: A = ½ × b × h
- A — area in square units (square feet if you measured in feet)
- L, W — length and width of the rectangle
- r — radius of the circle, half the diameter
- b, h — triangle base and its height, measured at a right angle to the base (not the slanted side)
To include waste and cost: Area to buy = A × (1 + waste% ÷ 100) and Cost = Area to buy × price per sq ft.
Unit conversions used
The calculator uses exact definitions: 1 foot = 0.3048 meters and 1 inch = 2.54 cm. That gives 1 sq ft = 144 sq in = 0.09290304 m², and 1 sq yd = 9 sq ft.
Worked example: flooring an L-shaped living room
A living room is L-shaped. Split it into two rectangles:
- Main part: 16 ft × 12 ft = 192 sq ft
- Nook: 8 ft 6 in × 5 ft → 8.5 × 5 = 42.5 sq ft
Total floor area = 192 + 42.5 = 234.5 sq ft.
The flooring is laid straight, so add 10% waste: 234.5 × 1.10 = 257.95 sq ft. Flooring comes in boxes, so round up to whole boxes — at 22 sq ft per box that is 257.95 ÷ 22 = 11.7, so buy 12 boxes.
At $3.49 per sq ft, the material costs about 257.95 × 3.49 ≈ $900.
How much waste to add
Waste covers cut-offs at walls, pattern matching and the odd damaged piece. These are common planning ranges used by installers; your product’s instructions take priority.
| Material / layout | Typical allowance |
|---|---|
| Laminate or vinyl plank, straight lay | 5–10% |
| Hardwood, straight lay | 7–10% |
| Tile, straight grid | 10% |
| Tile or plank, diagonal or herringbone | 15–20% |
| Carpet (seams and pattern match) | 10–15% |
| Sod | 5% |
Room size reference
Quick areas for common room sizes, so you can sanity-check your result.
| Room size | Square feet | Square yards | Square meters |
|---|---|---|---|
| 8 × 10 ft | 80 | 8.89 | 7.43 |
| 10 × 10 ft | 100 | 11.11 | 9.29 |
| 10 × 12 ft | 120 | 13.33 | 11.15 |
| 12 × 12 ft | 144 | 16.00 | 13.38 |
| 12 × 15 ft | 180 | 20.00 | 16.72 |
| 14 × 16 ft | 224 | 24.89 | 20.81 |
| 15 × 20 ft | 300 | 33.33 | 27.87 |
| 20 × 20 ft (two-car garage) | 400 | 44.44 | 37.16 |
Measuring tips that save a second trip to the store
- Measure wall to wall at floor level, not at the baseboard top — walls are rarely perfectly straight.
- Measure twice in different spots and use the larger number. Older rooms are often a little out of square.
- Break odd shapes into pieces. Any floor plan can be split into rectangles, triangles and circle segments; add the pieces together.
- Subtract only what will not be covered. Kitchen islands and built-in cabinets come off a flooring estimate; closets usually stay in.
- Round up when you buy. Materials are sold in boxes, rolls or pallets. Calculate the exact area, add waste, then round up to the next whole unit.
Need volume instead of area — for concrete, mulch or gravel? Use the Concrete Calculator or the Cubic Yard Calculator. Covering walls rather than floors? Try the Paint Calculator or Drywall Calculator.
Frequently asked questions
How do I calculate square footage of a room?
Measure the length and width in feet and multiply them. A 12 ft by 10 ft room is 12 × 10 = 120 square feet. For an L-shaped room, split it into two rectangles, find each area, and add them.
How do I convert feet and inches to square feet?
Turn the inches into a decimal of a foot first by dividing by 12. For example, 10 ft 6 in = 10 + 6 ÷ 12 = 10.5 ft. Then multiply length × width as usual. Or switch the unit menu to inches and enter the whole measurement in inches — the calculator converts for you.
How many square feet are in a square yard?
Nine. A square yard is 3 ft × 3 ft = 9 sq ft, so divide square feet by 9 to get square yards. Carpet is often priced per square yard.
How much extra flooring should I buy?
Most installers add 5–10% for straight layouts and 10–15% for diagonal or herringbone patterns, because cut pieces at the walls are wasted. Enter that percentage in the waste box to see how much to order.
How do I find the square footage of a circle?
Multiply π (about 3.1416) by the radius squared. The radius is half the diameter, so a 10 ft circle has a radius of 5 ft and an area of 3.1416 × 25 ≈ 78.5 sq ft.