How to calculate square footage
Square footage is the area of a flat surface measured in square feet — one square foot is a square 1 ft on each side. For a rectangle, multiply the length by the width, with both measured in feet:
A bedroom 12 ft long and 15 ft wide is 12 × 15 = 180 sq ft. If you measured in inches, divide the result by 144 (because 12 × 12 = 144 square inches in a square foot).
Formulas for other shapes
| Shape | Formula | Example |
|---|---|---|
| Rectangle or square | Length × Width | 12 × 15 ft = 180 sq ft |
| Circle | π × (Diameter ÷ 2)² | 10 ft circle = 78.54 sq ft |
| Triangle | Base × Height ÷ 2 | 10 ft base, 8 ft high = 40 sq ft |
| Trapezoid | (Side a + Side b) ÷ 2 × Height | (10 + 14) ÷ 2 × 8 = 96 sq ft |
L-shaped and irregular rooms
Divide the space into rectangles that don't overlap, measure each one, and add the areas. An L-shaped living room made of a 14 × 12 ft section and an 8 × 6 ft alcove is 168 + 48 = 216 sq ft. Use Add another area in the calculator to do this in one go — each part can be a different shape.
Converting square feet
- Square yards (used for carpet): divide square feet by 9.
- Square meters: multiply square feet by 0.0929.
- Acres (used for land): divide square feet by 43,560.
Common room sizes
| Room size | Square feet | Square yards | Square meters |
|---|---|---|---|
| 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 × 14 ft | 168 | 18.67 | 15.61 |
| 12 × 16 ft | 192 | 21.33 | 17.84 |
| 14 × 16 ft | 224 | 24.89 | 20.81 |
| 15 × 20 ft | 300 | 33.33 | 27.87 |
| 20 × 20 ft | 400 | 44.44 | 37.16 |
How much extra flooring should I buy?
Flooring is cut to fit walls, doorways and closets, so the material you buy is always more than the floor area. Typical allowances are:
- Laminate, vinyl plank and carpet: about 5–10% extra.
- Tile: 10% for straight layouts, 15% or more for diagonal or herringbone patterns.
- Hardwood: 5–10%, more if boards have defects you'll cut out.
Enter that percentage in the waste box and the calculator adds it to the total. Keep a spare box or two — matching a discontinued product later is hard.
Measuring tips
- Measure wall to wall at floor level, and round up to the nearest inch.
- Measure each room twice; walls are rarely perfectly parallel, so use the larger figure.
- Include closets when buying flooring, but leave out areas under fixed cabinets.
- For the square footage of a home, measure the finished living space only — garages, unfinished basements and open porches are normally listed separately.
Plan the whole job
Once you have the area, turn it into materials: tiles and boxes, gallons of paint, drywall sheets, or concrete for a slab. Not sure how to measure? Read how to measure a room.
Frequently asked questions
How do I calculate the square footage of a room?
Measure the length and width of the room in feet and multiply them. A 12 × 14 ft room is 168 sq ft. For irregular rooms, split the floor into rectangles, find each area, and add them together.
How many square feet are in an acre?
One acre is 43,560 square feet, which is about 4,047 square meters. To convert square feet to acres, divide by 43,560.
How do I convert square feet to square yards?
Divide square feet by 9, because one square yard is 3 ft × 3 ft. For example, 180 sq ft ÷ 9 = 20 square yards.
How do I calculate square footage in inches?
Multiply length × width in inches, then divide by 144. A 48 × 96 inch sheet is 4,608 square inches, or 32 sq ft.
What is the square footage of a circle?
Multiply π (about 3.1416) by the radius squared. A circular patio 12 ft across has a radius of 6 ft, so its area is 3.1416 × 36 = 113.10 sq ft.
Does square footage of a house include the garage?
Usually not. Listed home square footage normally counts finished, heated living space; garages, unfinished basements and porches are listed separately. Practices vary by region, so check local listing rules.
Sources & standards
This calculator's formulas and default values are based on the following codes, standards and published data. Codes are adopted and amended locally, so check with your building department for permitted work. See how we build and check our calculators.
- ANSI Z765, Single-Family Residential Buildings: Square Footage, Method for Calculating: the US standard for reporting home square footage.
- Standard geometric area formulas for rectangles, triangles, circles and trapezoids.
- NIST unit conversions: 1 ft² = 0.092903 m²; 1 acre = 43,560 ft².