How to use the square footage calculator
- Choose the shape that best matches the space.
- Enter the measurements in feet. Convert inches by dividing by 12: 3 in = 0.25 ft, 6 in = 0.5 ft, 9 in = 0.75 ft, so 12 ft 9 in is 12.75 ft.
- Optionally enter a price per square foot to estimate the cost of materials or installation.
Area formulas
| Shape | Formula | Example |
|---|---|---|
| Rectangle or square | length × width | 12 × 15 = 180 sq ft |
| Circle | π × radius², radius = diameter ÷ 2 | 10 ft across: 3.1416 × 5² ≈ 78.54 sq ft |
| Triangle | base × height ÷ 2 | 10 × 6 ÷ 2 = 30 sq ft |
| L-shape | rectangle A + rectangle B | 20 × 12 + 10 × 8 = 320 sq ft |
Measuring L-shaped and irregular rooms
Split the floor plan into rectangles that don't overlap, measure each one and add them up. For an L-shaped room, imagine extending one inside wall straight across the room: that divides the floor into a long rectangle and a short one. Measure the second rectangle only up to that line — if both rectangles run to the outer walls, the corner square gets counted twice.
More complicated spaces work the same way. Break them into rectangles, triangles and circles, calculate each part, add the results, and subtract areas you won't cover, such as a kitchen island or a fireplace hearth.
Worked example: flooring a living room
A living room measures 15 ft 6 in by 13 ft. Since 6 inches is 0.5 ft, the area is 15.5 × 13 = 201.5 sq ft, which is 22.39 square yards or 18.72 square meters. Laminate at $2.79 per square foot costs about $562 for that exact area. Flooring is normally bought with extra for cuts and mistakes; adding 10% gives 221.65 sq ft, so you would buy enough full cartons to cover at least 222 sq ft — about $618 at the same price.
Unit conversions
| Unit | Equals |
|---|---|
| 1 square yard | 9 square feet |
| 1 square meter | 10.764 square feet |
| 1 square foot | 144 square inches = 0.0929 m² |
| 1 acre | 43,560 square feet |
Carpet is often priced per square yard. Divide square feet by 9 to compare it with flooring priced per square foot, or divide the per-yard price by 9 to get a per-foot price.
Tips for common projects
- Flooring and tile: a common rule of thumb is 10% extra for straight layouts and more for diagonal or herringbone patterns, which waste more at the edges. Follow the manufacturer's guidance where it differs.
- Paint: you need wall area, not floor area. Multiply the room's perimeter by the wall height and subtract large doors and windows.
- Concrete, gravel and mulch: these are sold by volume, so you also need the depth. The concrete calculator converts a slab to cubic yards and bags.
- Measure twice: walls are rarely perfectly square. Measure each dimension at two or three points and use the largest.
Frequently asked questions
How do I calculate square footage?
For a rectangle, multiply the length by the width in feet. A room 11 ft by 14 ft is 154 square feet. For other shapes use the formulas in the table above.
How many square feet is a 12 by 12 room?
12 × 12 = 144 square feet, which is 16 square yards or about 13.4 square meters.
How do I convert square feet to square yards?
Divide by 9, because a square yard is 3 ft × 3 ft. 180 square feet is 20 square yards.
How do I include inches in my measurements?
Divide the inches by 12 and add them to the feet. 10 ft 4 in is 10 + 4 ÷ 12 = 10.33 ft. Alternatively, measure everything in inches, multiply, and divide the result by 144.
How do I find the area of a round space?
Measure the diameter, halve it to get the radius, then multiply π (about 3.1416) by the radius squared. A circular patio 12 ft across is 3.1416 × 36 ≈ 113.1 square feet.
Last updated: October 8, 2026