Square footage is the size of a flat surface measured in square feet. You need it to buy flooring, paint or sod, to compare homes for sale or rent, and to get fair quotes from contractors. This free sq ft calculator works it out for rectangles, L-shaped rooms, triangles, circles and trapezoids, shows the formula with your own numbers, and keeps a running total when you measure more than one space.
How to use this square footage calculator
- Choose a shape that matches your space. Most rooms are rectangles; open-plan areas are often L-shaped.
- Pick a unit. Feet + inches is the default, so you can type 12 ft 6 in exactly as you read it off the tape. You can also measure in inches, yards, metres or centimetres.
- Enter the measurements shown in the diagram. The answer updates as you type, in square feet, square metres, square yards, square inches and acres.
- Add options if you need them: a waste percentage for flooring or tile, and a price per square foot to estimate the total cost.
- Measuring several spaces? Name the area, tap Add to total and measure the next one. Tick Subtract for cut-outs such as a kitchen island or a fireplace hearth.
Tap Copy share link to save your work. The link stores every number you entered, so you can send it to a contractor or open it later on another device.
How to calculate square feet
To calculate square feet for a rectangle or square, multiply the length by the width, both in feet:
Square feet = length (ft) × width (ft)
If you measured in inches, multiply the two inch measurements and divide by 144, because one square foot holds 144 square inches (12 in × 12 in). If you measured in metres, multiply to get square metres, then multiply by 10.764 to get square feet.
Formulas for other shapes
| Shape | Formula | What to measure |
|---|---|---|
| Rectangle or square | Length × Width | Two sides that meet at a corner |
| L-shape | (A length × A width) + (B length × B width) | Split the L into two rectangles |
| Triangle | Base × Height ÷ 2 | The base and the height at a right angle |
| Triangle (3 sides) | √(s(s − a)(s − b)(s − c)), s = (a + b + c) ÷ 2 | All three sides (Heron’s formula) |
| Circle | π × (Diameter ÷ 2)² | Straight across through the centre |
| Trapezoid | (a + b) ÷ 2 × Height | Both parallel sides and the distance between them |
Worked example: square feet of a room
A living room measures 15 ft 6 in by 12 ft 3 in.
- Convert the inches to decimal feet: 6 ÷ 12 = 0.5, so 15.5 ft; 3 ÷ 12 = 0.25, so 12.25 ft.
- Multiply: 15.5 × 12.25 = 189.88 sq ft (about 190 sq ft).
- That equals 17.64 m², 21.1 sq yd or 27,342 sq in.
- For flooring at $4.50 per sq ft with 10% waste: 189.88 × 1.10 = 208.86 sq ft, so the material costs about $939.88.
Common room sizes in square feet
Use this table as a sense check. If a bedroom comes out at 1,400 sq ft, one measurement was probably typed in inches while the unit was set to feet.
| Room size | Square feet | Square metres | Typical use |
|---|---|---|---|
| 10 × 10 ft | 100 | 9.3 | Small bedroom, home office |
| 10 × 12 ft | 120 | 11.1 | Bedroom, nursery |
| 11 × 12 ft | 132 | 12.3 | Bedroom |
| 12 × 12 ft | 144 | 13.4 | Bedroom, dining room |
| 12 × 14 ft | 168 | 15.6 | Large bedroom, kitchen |
| 12 × 15 ft | 180 | 16.7 | Living room, primary bedroom |
| 12 × 16 ft | 192 | 17.8 | Family room, primary bedroom |
| 13 × 15 ft | 195 | 18.1 | Primary bedroom |
| 14 × 16 ft | 224 | 20.8 | Living room |
| 15 × 20 ft | 300 | 27.9 | Large living room |
| 16 × 20 ft | 320 | 29.7 | Great room, open-plan kitchen |
| 20 × 20 ft | 400 | 37.2 | Two-car garage |
Tips for accurate measurements
- Measure wall to wall at floor level, where the flooring will actually go, and round up to the nearest inch.
- Measure both pairs of walls. Rooms are rarely perfectly square. If opposite walls differ, use the longer figure when buying materials.
- Sketch the space first and write each measurement on the drawing. It is the easiest way to spot a missing alcove or closet.
- Use a laser measure for long rooms. A tape that sags over 20 feet can easily be an inch or two out.
- Split odd shapes into rectangles and triangles, then add them up with the running total.
Square feet to other units
- 1 square foot = 144 square inches = 0.111 square yards = 0.0929 square metres
- 1 square yard = 9 square feet
- 1 square metre = 10.764 square feet
- 1 acre = 43,560 square feet = 4,840 square yards
The calculator shows all of these at once, so you never have to convert by hand. Got another question? Browse the square footage FAQ or our measuring guides.
Frequently asked questions
How do I calculate square footage?
Measure the length and width of the space in feet and multiply them. A room 12 feet long and 10 feet wide is 12 × 10 = 120 square feet. For other shapes, use the matching formula or split the space into rectangles and add the areas together.
How many square feet is a 12×12 room?
A 12 × 12 foot room is 144 square feet, which is 13.38 square metres or 16 square yards.
How do I calculate square feet from inches?
Multiply the length in inches by the width in inches, then divide by 144. For example, 96 in × 120 in = 11,520 square inches, and 11,520 ÷ 144 = 80 square feet.
How do I work out square footage with feet and inches?
Turn the inches into a decimal of a foot by dividing by 12 (6 inches = 0.5 ft, 9 inches = 0.75 ft), then multiply as normal. Or choose Feet + inches in the calculator and type the feet and inches into separate boxes.
How do I find the square footage of an irregular room?
Divide the room into simple shapes such as rectangles and triangles, work out each area, then add them together. Use Add to total for each piece, and tick Subtract for areas you want to take away, such as a built-in island.
Is square footage the same as square feet?
Yes. Square footage is simply an area expressed in square feet. “The room’s square footage is 150” and “the room is 150 square feet” mean the same thing.
How do I calculate the cost of a project per square foot?
Multiply the area by the price per square foot. 200 sq ft of flooring at $3.50 per sq ft costs 200 × 3.50 = $700. To find a price per square foot from a total, divide the total cost by the area.
How much extra flooring should I buy?
Most installers add 5–10% for a straight layout and 15% or more for diagonal or herringbone patterns, to allow for cuts and mistakes. Enter this in the waste allowance box and the calculator adds it for you.