How to calculate square footage
Square footage is the area of a flat space measured in feet. For a plain rectangle, multiply the length by the width. A room that is 12 ft by 15 ft is 12 × 15 = 180 square feet. If your measurements are in inches, yards or meters, convert them to feet first, or pick the unit above and the calculator converts for you.
| Shape | Formula | Example | Area |
|---|---|---|---|
| Rectangle | length × width | 12 ft × 15 ft | 180 sq ft |
| L-shape | area 1 + area 2 | (12 × 10) + (5 × 4) | 140 sq ft |
| Triangle | ½ × base × height | ½ × 10 ft × 6 ft | 30 sq ft |
| Circle | π × (diameter ÷ 2)² | diameter 10 ft | 78.54 sq ft |
| Trapezoid | (top + bottom) ÷ 2 × height | (8 + 12) ÷ 2 × 5 | 50 sq ft |
How many square feet is my room?
These are the room sizes people search for most, worked out in square feet, square meters and square yards.
| Room size | Square feet | Square meters | Square yards |
|---|---|---|---|
| 8 × 10 ft | 80 | 7.43 | 8.89 |
| 10 × 10 ft (small bedroom or office) | 100 | 9.29 | 11.11 |
| 10 × 12 ft | 120 | 11.15 | 13.33 |
| 12 × 12 ft (average bedroom) | 144 | 13.38 | 16 |
| 12 × 15 ft | 180 | 16.72 | 20 |
| 15 × 20 ft | 300 | 27.87 | 33.33 |
| 20 × 20 ft | 400 | 37.16 | 44.44 |
| 24 × 24 ft (two-car garage) | 576 | 53.51 | 64 |
How to calculate the square footage of an L-shaped room
- Draw the room and split the L into two rectangles that do not overlap.
- Measure the length and width of each rectangle.
- Multiply length × width for each one: 12 × 10 = 120 sq ft and 5 × 4 = 20 sq ft.
- Add the two areas: 120 + 20 = 140 sq ft.
Choose the L-shape tab above and the calculator does the adding for you. For a room with more than two parts, work out each part and use Add room to total.
Square feet to square meters, square yards and acres
One square foot is exactly 0.09290304 square meters, because one foot is exactly 0.3048 meters. There are 9 square feet in a square yard and 43,560 square feet in an acre. For more values see the square feet to square meters converter.
| Area | Square meters | Square yards | Acres |
|---|---|---|---|
| 100 sq ft | 9.29 m² | 11.11 | 0.0023 |
| 250 sq ft | 23.23 m² | 27.78 | 0.0057 |
| 500 sq ft | 46.45 m² | 55.56 | 0.0115 |
| 750 sq ft | 69.68 m² | 83.33 | 0.0172 |
| 1,000 sq ft | 92.9 m² | 111.11 | 0.023 |
| 1,500 sq ft | 139.35 m² | 166.67 | 0.0344 |
| 2,000 sq ft | 185.81 m² | 222.22 | 0.0459 |
| 2,500 sq ft | 232.26 m² | 277.78 | 0.0574 |
| 3,000 sq ft | 278.71 m² | 333.33 | 0.0689 |
| 5,000 sq ft | 464.52 m² | 555.56 | 0.1148 |
How much flooring, tile or paint do I need?
Start with the plain floor area, then add extra for cuts and breakage. Open Waste and cost above, enter a waste percentage and a price per square foot, and the calculator shows the amount to order and a cost estimate. For example, 144 sq ft with 10% waste is 158.4 sq ft. Many installers add roughly 5–10% for a simple layout and more for diagonal or patterned floors, so check the installation guide for your product.
For wall paint, measure the distance around the room (the perimeter), multiply by the wall height, then subtract large openings such as doors and windows. Divide by the coverage printed on the paint can.
Square feet vs linear feet
Square feet measure area; linear feet measure length. A 12 ft baseboard is 12 linear feet, while a 12 × 12 ft room is 144 square feet. Buy flooring, tile and carpet by square foot, and trim and lumber by linear foot.
How is the square footage of a house measured?
For homes, the American National Standard ANSI Z765-2020 sets out a method for calculating the square footage of single-family houses (Home Innovation Research Labs). Listings and appraisals do not always follow it, and they usually count only finished living space. For a flooring or paint project, measure the rooms you are working on yourself, as this calculator does.
Frequently asked questions
How do I calculate the square footage of a room?
Measure the longest length and the widest width in feet and multiply them. A 12 × 15 ft room is 180 sq ft. If the room is not a plain rectangle, split it into rectangles, work out each one and add them together. The calculator above does this for you, including L-shapes.
How many square feet is a 12x12 room?
A 12 × 12 ft room is 144 square feet (12 × 12 = 144). A 10 × 10 room is 100 sq ft, a 10 × 12 room is 120 sq ft and a 20 × 20 room is 400 sq ft.
How do I calculate the square footage of an L-shaped room?
Split the L into two rectangles that do not overlap, multiply length by width for each, and add the two areas. For example, 12 × 10 ft plus 5 × 4 ft is 120 + 20 = 140 sq ft. Choose the L-shape tab and enter both sections.
What is the difference between square feet and linear feet?
Square feet measure area, the flat space a floor or wall covers. Linear feet measure length in a straight line. Flooring, tile, carpet and paint are bought by the square foot. Baseboard, trim and lumber are usually bought by the linear foot. A 12 ft wall is 12 linear feet; a 12 × 12 ft room is 144 square feet.
How do I convert square feet to square meters, square yards and acres?
Multiply square feet by 0.09290304 for square meters, divide by 9 for square yards and divide by 43,560 for acres. The calculator shows all three automatically. For a longer list see the square feet to square meters converter.
How much extra should I order for waste?
Cuts, pattern matching and breakage mean you need more material than the plain floor area. Many installers add roughly 5–10% for a simple straight layout and more for diagonal or patterned layouts. Enter your waste percentage in the options above, and check the installation guide for your product. For 144 sq ft with 10% waste you would order 158.4 sq ft.
Does this calculator upload my measurements?
No. The maths runs in your browser. Nothing you type is sent to a server, there is no signup, and it works offline once the page has loaded.
Written by Prakhar Singh, software engineer and creator of K4Converter · Last updated November 2026