Square Footage Calculator
Result
Square feet
- Square meters
- 11.15 m²
- Square yards
- 13.33 yd²
The square footage calculator multiplies length by width for one or two rectangles and reports the floor area in square feet, square meters and square yards. Most rooms are a rectangle, and an L-shaped plan is just two of them, so a bedroom with an alcove or a sitting area off a hallway can be measured without drawing anything. Enter each side in feet, inches, yards, meters or centimeters — the tool converts to feet first — and leave the second rectangle at zero when the space is a single room.
Typical US room sizes and their floor area
| Width (ft) | Length (ft) | Area (ft²) |
|---|---|---|
| 8 | 10 | 80 |
| 10 | 12 | 120 |
| 12 | 12 | 144 |
| 12 | 15 | 180 |
| 15 | 20 | 300 |
| 20 | 20 | 400 |
Room dimensions vary by plan; these are the sizes you will see most often in listings and floor plans. Add 10% for offcuts and mistakes before ordering flooring.
Formula
Area = length × width + length₂ × width₂
- length
- Length of the first rectangle
- width
- Width of the first rectangle
- length₂
- Length of the second rectangle, 0 if unused
- width₂
- Width of the second rectangle, 0 if unused
Use it for floor area: flooring, tile, a rug, or paint on a wall that is one rectangle tall. Both rectangles must be right-angled and must not overlap. A curved bay or a diagonal wall has to be split into rectangles by hand, and the answer will be an approximation rather than an exact area.
Worked examples
A 12 ft × 10 ft bedroom
- Multiply the two sides: 12 × 10 = 120
- The second rectangle is 0, so there is nothing to add
- Into square meters: 120 × 0.092903 = 11.15 m²
- Into square yards: 120 ÷ 9 = 13.33 yd²
Worth knowing before you order flooring: carpet is sold by the square yard in the US, so 120 ft² is 13.33 yd² — and you would round up to 14.
A living room with an alcove
- First rectangle: 20 × 15 = 300
- Second rectangle: 8 × 6 = 48
- Add them: 300 + 48 = 348 ft²
- Into square meters: 348 × 0.092903 = 32.33 m²
Fill in one side of the second rectangle and leave the other at 0 and the tool stops with an error instead of quietly dropping the alcove from the total.
Limitations
Square footage is floor area, so ceiling height and wall area never enter — a 12 × 10 room has 120 ft² of floor whether the ceiling is 8 ft or 12 ft. Nothing is subtracted for what you cannot walk on: a chimney breast, a stairwell, a closet or a kitchen island all keep their full share unless you take them out yourself. Keep one measurement in one unit: 12 ft 6 in is 12.5 ft, not 12.6.
Frequently asked questions
- How do I calculate square footage?
- Multiply the length by the width, both in feet. A room 12 ft by 10 ft is 120 ft². If the space is L-shaped, split it into two rectangles, work out each one and add them: 20 × 15 plus 8 × 6 is 300 + 48, so 348 ft². That is the whole method — the tool exists to do the unit conversion and the adding.
- How many square feet is a 12 × 12 room?
- 144 ft², which is 13.38 square meters and 16 square yards exactly. A 12 × 12 room is the classic US secondary bedroom, and 144 ft² is a common minimum in floor plans for one.
- How do I convert square feet to square meters?
- Divide the square feet by 10.7639, or multiply by 0.092903. 500 ft² is 46.45 m². Going the other way, multiply square meters by 10.7639: a 100 m² apartment is about 1,076 ft², which is why listings that say 1,200 sq ft are describing something close to 111 m².
- Do closets and hallways count as floor area?
- They are real floor area, so they belong in a flooring order — you will be laying material there. But if you are sizing a rug, planning where furniture goes, or comparing two apartments, leave them out, because the number you want is usable room area.
- Why does the second section throw an error when I fill in only one side?
- One side does not describe a rectangle, and the tool cannot tell whether you meant an 8 ft wall or forgot the other measurement. Both sides of the second rectangle, or both at 0. A total that silently ignored what you typed would send you to the store short of flooring.
References
- NIST Guide to the SI, Special Publication 811 — US National Institute of Standards and Technology
- The International System of Units (SI Brochure) — Bureau International des Poids et Mesures